diff --git a/2021/01.rkt b/2021/01.rkt
new file mode 100644
index 0000000..7b6091f
--- /dev/null
+++ b/2021/01.rkt
@@ -0,0 +1,20 @@
+#lang br
+(require racket/file rackunit)
+
+(define depths (map string->number (file->lines "01.rktd")))
+
+(define (positive-deltas depths)
+  (filter positive?
+          (for/list ([d1 (in-list depths)]
+                     [d2 (in-list (cdr depths))])
+            (- d2 d1))))
+
+(check-equal? (length (positive-deltas depths)) 1167)
+
+(define (trios depths)
+  (for/list ([d1 (in-list depths)]
+             [d2 (in-list (cdr depths))]
+             [d3 (in-list (cddr depths))])
+    (+ d1 d2 d3)))
+
+(check-equal? (length (positive-deltas (trios depths))) 1130)
\ No newline at end of file
diff --git a/2021/01.rktd b/2021/01.rktd
new file mode 100644
index 0000000..ad0a3bd
--- /dev/null
+++ b/2021/01.rktd
@@ -0,0 +1,2000 @@
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diff --git a/2021/02.rkt b/2021/02.rkt
new file mode 100644
index 0000000..62fb2a7
--- /dev/null
+++ b/2021/02.rkt
@@ -0,0 +1,32 @@
+#lang br
+(require racket/file sugar/list rackunit)
+
+(define instructions
+  (slice-at (for/list ([datum (in-port read (open-input-file "02.rktd"))])
+              datum) 2))
+
+(define (solve matcher)
+  (for/fold ([pos 0]
+             [depth 0]
+             [aim 0]
+             #:result (* pos depth))
+            ([i (in-list instructions)])
+    (matcher pos depth aim i)))
+
+(define (solve-1)
+  (solve (λ (pos depth aim i)
+           (match i
+             [(list 'forward amt) (values (+ pos amt) depth aim)]
+             [(list 'down amt) (values pos (+ depth amt) aim)]
+             [(list 'up amt) (values pos (- depth amt) aim)]))))
+
+(check-equal? (solve-1) 1488669)
+
+(define (solve-2)
+  (solve (λ (pos depth aim i)
+           (match i
+             [(list 'forward amt) (values (+ pos amt) (+ depth (* aim amt)) aim)]
+             [(list 'down amt) (values pos depth (+ aim amt))]
+             [(list 'up amt) (values pos depth (- aim amt))]))))
+
+(check-equal? (solve-2) 1176514794)
\ No newline at end of file
diff --git a/2021/02.rktd b/2021/02.rktd
new file mode 100644
index 0000000..e638be8
--- /dev/null
+++ b/2021/02.rktd
@@ -0,0 +1,1000 @@
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diff --git a/2021/03.rkt b/2021/03.rkt
new file mode 100644
index 0000000..69d8814
--- /dev/null
+++ b/2021/03.rkt
@@ -0,0 +1,40 @@
+#lang br
+(require racket/file rackunit)
+
+(define lines (map string->list (file->lines "03.rktd")))
+(define (digit-columns lines) (apply map list lines))
+
+(define (most-common-digit chars)
+  (define zeroes (count (λ (c) (char=? c #\0)) chars))
+  (define most-threshold (/ (length chars) 2))
+  (cond
+    [(= zeroes most-threshold) #f]
+    [(> zeroes most-threshold) #\0]
+    [else #\1]))
+
+(define (least-common-digit chars)
+  (match (most-common-digit chars)
+    [#false #false]
+    [#\0 #\1]
+    [_ #\0]))
+
+(define (chars->binary-number chars)
+  (string->number (list->string chars) 2))
+
+(define gamma-rate (chars->binary-number (map most-common-digit (digit-columns lines))))
+(define epsilon-rate (chars->binary-number (map least-common-digit (digit-columns lines))))
+
+(check-equal? (* gamma-rate epsilon-rate) 4174964)
+
+(define (find-digit proc default)
+    (for/fold ([lines lines]
+             #:result (chars->binary-number (car lines)))
+            ([i (in-range (length (car lines)))]
+             #:break (= (length lines) 1))
+    (define target (or (proc (list-ref (digit-columns lines) i)) default))
+    (filter (λ (line) (char=? (list-ref line i) target)) lines)))
+
+(define oxygen-rate (find-digit most-common-digit #\1))
+(define co2-rate (find-digit least-common-digit #\0))
+
+(check-equal? (* oxygen-rate co2-rate) 4474944)
\ No newline at end of file
diff --git a/2021/03.rktd b/2021/03.rktd
new file mode 100644
index 0000000..7948050
--- /dev/null
+++ b/2021/03.rktd
@@ -0,0 +1,1000 @@
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diff --git a/2021/04.rkt b/2021/04.rkt
new file mode 100644
index 0000000..31741b4
--- /dev/null
+++ b/2021/04.rkt
@@ -0,0 +1,43 @@
+#lang br
+(require racket/file sugar rackunit)
+
+(define lines (file->lines "04.rktd"))
+
+(define numbers-to-draw (map string->number (string-split (string-replace (car lines) "," " "))))
+
+(define boards
+  (map list->vector (slice-at (map string->number (string-split (string-join (cdr lines)))) 25)))
+
+(define winning-lines
+  (let ()
+    (define rows '((0 1 2 3 4) (5 6 7 8 9) (10 11 12 13 14) (15 16 17 18 19) (20 21 22 23 24)))
+    (define cols (apply map list rows))
+    (append rows cols)))
+
+(define (board-wins board)
+  (for/or ([winning-line winning-lines])
+    (for/and ([idx winning-line])
+      (eq? (vector-ref board idx) #true))))
+
+(define (run-game boards)
+  (for*/fold ([boards boards]
+              [winners null]
+              #:result (reverse winners))
+             ([number numbers-to-draw]
+              #:break (empty? boards))
+    (for ([board boards])
+      (define pos-of-number (vector-member number board))
+      (when pos-of-number
+        (vector-set! board pos-of-number #true)))
+    (define-values (new-winners losers) (partition board-wins boards))
+    (values losers (append (for/list ([winner new-winners])
+                             (cons number winner)) winners))))
+
+(define (calc-score res)
+  (match res
+    [(cons last-number board) (* last-number (apply + (filter number? (vector->list board))))]))
+
+(define results (run-game boards))
+(check-equal? (calc-score (first results)) 64084)
+(check-equal? (calc-score (last results)) 12833)
+
diff --git a/2021/04.rktd b/2021/04.rktd
new file mode 100644
index 0000000..ee55530
--- /dev/null
+++ b/2021/04.rktd
@@ -0,0 +1,601 @@
+27,14,70,7,85,66,65,57,68,23,33,78,4,84,25,18,43,71,76,61,34,82,93,74,26,15,83,64,2,35,19,97,32,47,6,51,99,20,77,75,56,73,80,86,55,36,13,95,52,63,79,72,9,10,16,8,69,11,50,54,81,22,45,1,12,88,44,17,62,0,96,94,31,90,39,92,37,40,5,98,24,38,46,21,30,49,41,87,91,60,48,29,59,89,3,42,58,53,67,28
+
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diff --git a/2021/05.rkt b/2021/05.rkt
new file mode 100644
index 0000000..9cc368e
--- /dev/null
+++ b/2021/05.rkt
@@ -0,0 +1,38 @@
+#lang br
+(require racket/file sugar rackunit racket/set)
+
+(define lines (map (λ (s) (map (λ (s2) (define ints (map string->number (string-split s2 ",")))
+                                 (+ (first ints) (* +i (second ints)))) (string-split s " -> "))) (file->lines "05.rktd")))
+
+(define (Line-not-diagonal line)
+  (match line
+    [(list left right) (or (= (real-part left) (real-part right)) (= (imag-part left) (imag-part right)))]))
+
+;; why does make-polar cause the solution to run faster?
+;; both functions create an imaginary number
+;; make-polar is slower to create the numbers (because it has to call trig functions)
+;; but storing the polar numbers with frequency-hash is much faster
+;; using inexact coefficients makes make-rectangular go faster
+;; but still not as fast as make-polar
+(define go-fast? #true)
+(define imag-func (if go-fast? make-polar make-rectangular))
+
+(define (expand line)
+  (match-define (list x1 x2) (map real-part line))
+  (match-define (list y1 y2) (map imag-part line))
+  (cond
+    [(= x1 x2)
+     (for/list ([i (in-range (apply min (list y1 y2)) (add1 (apply max (list y1 y2))))])
+       (imag-func x1 i))]
+    [(= y1 y2)
+     (for/list ([i (in-range (apply min (list x1 x2)) (add1 (apply max (list x1 x2))))])
+       (imag-func i y1))]
+    [else (for/list ([x (in-range x1 ((if (> x1 x2) sub1 add1) x2) (if (> x1 x2) -1 1))]
+                     [y (in-range y1 ((if (> y1 y2) sub1 add1) y2) (if (> y1 y2) -1 1))])
+            (imag-func x y))]))
+
+(define (calc-result points)
+  (length (filter (λ (x) (>= x 2)) (hash-values (time (frequency-hash points))))))
+
+(check-equal? (calc-result (append-map expand (filter Line-not-diagonal lines))) 6113)
+(check-equal? (calc-result (append-map expand lines)) 20373)
\ No newline at end of file
diff --git a/2021/05.rktd b/2021/05.rktd
new file mode 100644
index 0000000..323dd59
--- /dev/null
+++ b/2021/05.rktd
@@ -0,0 +1,500 @@
+309,347 -> 309,464
+425,687 -> 300,687
+226,766 -> 885,107
+681,618 -> 921,378
+968,54 -> 38,984
+35,341 -> 321,627
+493,485 -> 632,485
+908,183 -> 110,981
+677,378 -> 677,231
+703,378 -> 703,536
+179,581 -> 429,331
+339,133 -> 664,458
+212,680 -> 212,136
+251,699 -> 858,699
+163,725 -> 163,22
+70,226 -> 97,226
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+431,467 -> 499,399
+434,306 -> 304,436
+774,618 -> 521,618
+364,426 -> 364,457
+44,849 -> 791,102
+70,850 -> 276,850
+181,838 -> 181,736
+574,18 -> 574,784
+103,613 -> 537,179
+34,218 -> 115,299
+808,777 -> 636,777
+483,112 -> 483,939
+15,790 -> 15,253
+433,427 -> 742,427
+829,947 -> 895,947
+361,180 -> 860,180
+124,499 -> 124,615
+879,712 -> 745,712
+16,12 -> 16,149
+36,981 -> 36,561
+929,52 -> 30,951
+845,85 -> 318,612
+114,731 -> 794,51
+434,280 -> 406,308
+530,513 -> 114,513
+417,715 -> 417,273
+44,845 -> 44,225
+951,122 -> 450,623
+32,707 -> 32,832
+51,58 -> 51,806
+165,305 -> 49,189
+517,221 -> 942,221
+125,233 -> 193,233
+903,180 -> 101,982
+123,303 -> 247,179
+199,174 -> 546,521
+185,860 -> 538,860
+825,751 -> 825,784
+454,720 -> 64,720
+28,10 -> 974,956
+626,760 -> 586,760
+91,234 -> 10,234
+973,939 -> 65,31
+589,308 -> 255,308
+547,945 -> 239,945
+909,914 -> 111,116
+484,182 -> 253,182
+145,575 -> 339,575
+215,143 -> 611,143
+963,983 -> 20,40
+220,733 -> 333,846
+126,860 -> 940,46
+715,823 -> 715,284
+832,65 -> 436,65
+923,496 -> 530,889
+708,517 -> 708,764
+154,681 -> 22,549
+909,135 -> 57,987
+225,966 -> 225,941
+629,491 -> 629,17
+927,349 -> 72,349
+15,987 -> 983,19
+265,912 -> 74,912
+14,985 -> 988,11
+986,64 -> 129,921
+697,831 -> 943,831
+379,143 -> 853,617
+232,887 -> 623,887
+947,473 -> 947,453
+898,762 -> 218,762
+599,386 -> 870,386
+757,137 -> 757,496
+437,285 -> 437,326
+515,311 -> 515,63
+305,703 -> 720,703
+321,770 -> 88,537
+75,48 -> 457,430
+38,499 -> 38,544
+481,896 -> 481,944
+614,483 -> 437,483
+647,430 -> 368,430
+641,669 -> 641,691
+849,626 -> 427,204
+805,688 -> 805,536
+102,315 -> 102,108
+729,525 -> 770,525
+234,702 -> 38,702
+17,457 -> 526,457
+369,155 -> 369,647
+216,118 -> 216,43
+342,384 -> 342,905
+470,832 -> 314,676
+179,318 -> 179,315
+40,707 -> 547,707
+771,236 -> 453,236
+113,823 -> 826,110
+731,642 -> 707,642
+36,398 -> 810,398
+233,447 -> 979,447
+74,286 -> 907,286
+939,223 -> 939,10
+866,57 -> 866,656
+978,20 -> 10,988
+816,176 -> 50,942
+293,868 -> 293,350
+900,159 -> 148,911
+58,84 -> 644,84
+720,416 -> 720,906
+935,31 -> 13,953
+41,727 -> 221,727
+633,112 -> 633,695
+418,947 -> 418,574
+632,711 -> 791,711
+73,228 -> 73,861
+59,447 -> 83,447
+418,938 -> 418,638
+922,352 -> 636,352
+66,773 -> 66,868
+69,678 -> 600,147
+333,251 -> 298,251
+371,803 -> 740,434
+976,972 -> 976,165
+896,415 -> 240,415
+672,476 -> 860,476
+202,291 -> 195,291
+99,971 -> 518,552
+284,858 -> 910,232
+187,282 -> 187,627
+157,445 -> 157,665
+421,879 -> 38,496
+155,431 -> 405,431
+772,472 -> 315,929
+69,818 -> 132,818
+70,328 -> 70,800
+471,788 -> 646,788
+960,900 -> 97,37
+258,566 -> 186,494
+345,413 -> 306,413
+897,173 -> 897,896
+74,740 -> 74,795
+679,238 -> 679,811
+870,64 -> 64,870
+30,869 -> 288,869
+539,380 -> 539,862
+452,692 -> 748,692
+527,712 -> 527,139
+725,504 -> 717,504
+201,338 -> 636,338
+626,719 -> 626,302
+580,153 -> 274,459
+654,215 -> 246,215
+363,738 -> 363,192
+335,502 -> 970,502
+266,52 -> 266,442
+125,127 -> 281,127
diff --git a/2021/06.rkt b/2021/06.rkt
new file mode 100644
index 0000000..46a4c09
--- /dev/null
+++ b/2021/06.rkt
@@ -0,0 +1,18 @@
+#lang br
+(require racket/file sugar rackunit)
+
+(define fish (map string->number (string-split (file->string "06.rktd") ",")))
+
+(define (simulate fish days)
+  (for/fold ([freqs (frequency-hash fish)]
+             #:result (apply + (hash-values freqs)))
+            ([d (in-range days)])
+    (hash-set*
+     (for/hasheq ([(k v) (in-hash freqs)]
+                  #:unless (zero? k))
+       (values (sub1 k) v))
+     6 (+ (hash-ref freqs 7 0) (hash-ref freqs 0 0))
+     8 (hash-ref freqs 0 0))))
+
+(check-equal? (simulate fish 80) 361169)
+(check-equal? (simulate fish 256) 1634946868992)
\ No newline at end of file
diff --git a/2021/06.rktd b/2021/06.rktd
new file mode 100644
index 0000000..a2ca78e
--- /dev/null
+++ b/2021/06.rktd
@@ -0,0 +1 @@
+1,1,3,5,3,1,1,4,1,1,5,2,4,3,1,1,3,1,1,5,5,1,3,2,5,4,1,1,5,1,4,2,1,4,2,1,4,4,1,5,1,4,4,1,1,5,1,5,1,5,1,1,1,5,1,2,5,1,1,3,2,2,2,1,4,1,1,2,4,1,3,1,2,1,3,5,2,3,5,1,1,4,3,3,5,1,5,3,1,2,3,4,1,1,5,4,1,3,4,4,1,2,4,4,1,1,3,5,3,1,2,2,5,1,4,1,3,3,3,3,1,1,2,1,5,3,4,5,1,5,2,5,3,2,1,4,2,1,1,1,4,1,2,1,2,2,4,5,5,5,4,1,4,1,4,2,3,2,3,1,1,2,3,1,1,1,5,2,2,5,3,1,4,1,2,1,1,5,3,1,4,5,1,4,2,1,1,5,1,5,4,1,5,5,2,3,1,3,5,1,1,1,1,3,1,1,4,1,5,2,1,1,3,5,1,1,4,2,1,2,5,2,5,1,1,1,2,3,5,5,1,4,3,2,2,3,2,1,1,4,1,3,5,2,3,1,1,5,1,3,5,1,1,5,5,3,1,3,3,1,2,3,1,5,1,3,2,1,3,1,1,2,3,5,3,5,5,4,3,1,5,1,1,2,3,2,2,1,1,2,1,4,1,2,3,3,3,1,3,5
\ No newline at end of file
diff --git a/2021/07.rkt b/2021/07.rkt
new file mode 100644
index 0000000..76485e7
--- /dev/null
+++ b/2021/07.rkt
@@ -0,0 +1,13 @@
+#lang br
+(require racket/file sugar rackunit)
+
+(define posns (map string->number (string-split (file->string "07.rktd") ",")))
+
+(define/caching (gauss-summation x) (* (/ x 2) (+ x 1)))
+
+(define (fuel-cost alignment [post-proc values])
+  (foldl (λ (posn res) (+ res (post-proc (abs (- alignment posn))))) 0 posns))
+
+(define possible-alignments (remove-duplicates posns))
+(check-equal? (apply min (map fuel-cost possible-alignments)) 349357)
+(check-equal? (apply min (map (λ (pa) (fuel-cost pa gauss-summation)) possible-alignments)) 96708205)
\ No newline at end of file
diff --git a/2021/07.rktd b/2021/07.rktd
new file mode 100644
index 0000000..a7eb16b
--- /dev/null
+++ b/2021/07.rktd
@@ -0,0 +1 @@
+1101,1,29,67,1102,0,1,65,1008,65,35,66,1005,66,28,1,67,65,20,4,0,1001,65,1,65,1106,0,8,99,35,67,101,99,105,32,110,39,101,115,116,32,112,97,115,32,117,110,101,32,105,110,116,99,111,100,101,32,112,114,111,103,114,97,109,10,33,133,43,1060,890,12,15,136,42,25,96,694,522,893,204,204,1168,311,1046,1699,26,399,299,66,644,402,65,480,711,72,894,244,249,337,331,774,126,23,484,1299,662,404,235,86,1492,556,73,478,210,82,433,597,154,130,178,491,578,856,532,1191,544,256,831,252,1001,109,37,1290,317,376,22,742,496,930,118,28,376,73,247,942,895,38,675,138,387,203,271,104,65,1099,981,167,67,57,607,1095,202,225,1067,1757,324,127,785,266,518,135,914,1006,1402,578,28,548,211,673,302,525,208,115,92,514,518,71,1298,796,780,166,1341,475,273,101,1155,838,1219,901,727,497,168,543,416,174,31,755,865,106,358,236,186,369,550,465,617,375,535,1639,513,419,1377,1024,704,77,38,0,149,5,28,1163,149,1654,614,1201,89,1141,844,1390,1081,132,1385,52,1027,80,572,377,340,39,630,875,692,289,339,358,68,205,54,149,41,1208,1528,171,204,438,571,308,556,1372,426,204,18,31,51,40,287,1845,1721,441,240,875,901,328,800,341,59,530,134,275,11,7,7,1,1571,218,374,536,992,464,234,398,300,74,99,1163,1039,430,43,659,667,1115,407,257,717,657,249,46,109,734,67,1010,581,1070,738,478,621,183,224,1372,560,1573,1026,338,485,1138,1007,910,16,846,556,423,200,962,103,570,540,900,839,319,171,14,22,205,225,569,81,381,132,127,139,123,788,1571,35,830,65,677,1745,819,804,854,346,190,480,1500,76,1049,306,17,668,113,163,755,1015,718,1037,156,267,158,74,377,26,294,203,334,1186,88,384,853,404,290,135,620,668,234,1158,2,1102,137,884,287,15,638,1003,187,24,534,24,647,683,934,275,1844,887,1746,1614,1788,632,100,332,1565,1352,341,1027,475,958,289,1564,89,1138,233,535,790,990,863,889,45,44,169,251,522,11,41,104,45,828,1206,1515,645,39,544,382,1413,995,188,310,51,39,474,14,7,1387,809,428,77,8,867,1105,718,426,146,486,191,1251,677,1139,802,585,1140,46,39,128,867,49,33,198,731,349,661,296,103,22,444,1198,1149,188,245,492,1147,230,213,300,551,295,1313,365,975,587,1416,1213,233,257,631,564,876,434,1353,51,748,1179,1428,915,115,57,90,1312,892,200,1349,35,1010,445,619,1261,108,14,1424,481,381,209,154,23,972,646,593,6,289,171,543,97,28,401,290,298,14,37,1326,1177,533,67,75,294,328,527,449,455,176,345,226,729,210,55,45,0,834,887,123,1326,931,278,449,1278,608,217,411,143,447,16,1043,29,165,88,860,582,21,811,920,162,1788,15,423,1172,842,801,845,20,155,155,642,40,1036,560,348,689,328,505,84,1013,58,93,1653,233,233,383,380,84,617,1128,305,123,508,205,6,322,118,359,1186,84,677,640,80,1357,868,1035,8,64,995,1246,266,443,346,112,523,625,206,66,565,1878,25,1277,936,283,148,987,282,368,883,542,631,946,118,53,4,235,16,950,4,998,106,25,151,1013,27,1038,77,140,82,1119,236,125,947,1446,680,301,301,936,21,609,516,280,264,281,108,43,215,36,126,401,402,693,360,321,92,1809,305,551,86,77,278,81,524,400,1458,1342,897,49,35,518,288,655,91,398,38,251,647,79,400,151,520,459,960,425,663,298,584,90,533,690,610,755,56,19,21,244,548,1116,773,43,115,171,1127,103,1199,1470,176,451,693,65,186,262,963,137,1422,431,533,210,799,17,388,600,1113,2,181,815,1153,6,618,590,719,196,39,301,424,193,560,175,351,279,603,171,423,146,158,48,398,513,115,1,1051,817,200,473,143,261,435,856,1057,503,51,846,1020,177,1091,232,500,372,475,70,485,1227,1032,64,743,299,159,1077,18,204,944,1075,29,78,63,67,9,1007,354,1046,491,448,206,222,121,955,290,381,147,146,104,576,722,163,715,1475,130,1104,586,97,352,173,713,315,1482,1221,38,10,81,457,745,323,47,197,1012,1593,128,463,373,272,90,121,1248,1451,540,681,63,950,19,208,230,1362,1225,1500,207,81,739,288,626,261,1188,356,889,408,3,368,94,858,1512,834,43,5,833,826,33,791,800,39,299,1587,41,783,498,899,296,1189,470,66,307,892,47,207,199,902,17,14,1831,11,576,729,1436,153,142,81,165,214,1543,1464,561,737,180,162,515,867,65,74,200,9,11,539,19,305,996,334,297,1825,427,169,225,53,688,420,623,111,313,324,5,376,433,135,308,94
\ No newline at end of file
diff --git a/2021/08.rkt b/2021/08.rkt
new file mode 100644
index 0000000..5a2b159
--- /dev/null
+++ b/2021/08.rkt
@@ -0,0 +1,71 @@
+#lang br
+(require racket/file rackunit racket/dict)
+
+(define (parse-ints strs) (map (λ (str) (string-split str)) strs))
+
+(define recs
+  (let* ([lines (string-split (file->string "08.rktd") "\n")]
+         [sublines (map (λ (str) (string-split str "|")) lines)])
+    (map parse-ints sublines)))
+
+(define strlens (append-map (λ (vals) (map string-length vals)) (map second recs)))
+(check-equal? (count (λ (len) (memq len '(2 3 4 7))) strlens) 278)
+
+(require csp racket/set)
+
+(define (infer-config #:one one-digit #:four four-digit #:seven seven-digit #:five five-segment-digits)
+  (define prob (make-csp))
+  (add-vars! prob '(s1 s2 s3 s4 s5 s6 s7) '(a b c d e f g))
+  (add-all-diff-constraint! prob #:same eq?)
+  (add-constraint! prob  (λ (s3 s6) (equal? (set s3 s6) one-digit)) '(s3 s6))
+  (add-constraint! prob 
+                   (λ (s1 s2 s3 s4 s5 s6 s7)
+                     (define two-pattern (set s1 s3 s4 s5 s7))
+                     (define three-pattern (set s1 s3 s4 s6 s7))
+                     (define five-pattern (set s1 s2 s4 s6 s7))
+                     (for/and ([pat (list two-pattern three-pattern five-pattern)])
+                       (member pat five-segment-digits)))
+                   '(s1 s2 s3 s4 s5 s6 s7))
+  (add-constraint! prob (λ (s2 s3 s4 s6) (equal? (set s2 s3 s4 s6) four-digit)) '(s2 s3 s4 s6))
+  (add-constraint! prob (λ (s1 s3 s6) (equal? (set s1 s3 s6) seven-digit)) '(s1 s3 s6))
+  (solve prob))
+
+(define segments-table (list
+                        (cons (set 's1 's2 's3 's5 's6 's7) 0)
+                        (cons (set 's3 's6) 1)
+                        (cons (set 's1 's3 's4 's5 's7) 2)
+                        (cons (set 's1 's3 's4 's6 's7) 3)
+                        (cons (set 's2 's3 's4 's6) 4)
+                        (cons (set 's1 's2 's4 's6 's7) 5)
+                        (cons (set 's1 's2 's4 's5 's6 's7) 6)
+                        (cons (set 's1 's3 's6) 7)
+                        (cons (set 's1 's2 's3 's4 's5 's6 's7) 8)
+                        (cons (set 's1 's2 's3 's4 's6 's7) 9)))
+
+(define (string->symbols str) (map (λ (c) (string->symbol (string c))) (string->list str)))
+
+(define (wire-config strs)
+  (define encdoded-digits (map (compose1 list->set string->symbols) strs))
+  (define (filter-length len) (filter (λ (x) (= len (set-count x))) encdoded-digits))
+  (define one-digit (car (filter-length 2)))
+  (define four-digit (car (filter-length 4)))
+  (define seven-digit (car (filter-length 3)))
+  (define five-segment-digits (filter-length 5))
+  (infer-config #:one one-digit #:four four-digit #:seven seven-digit #:five five-segment-digits))
+
+(define (decode-number config pattern)
+  (define config-reverse (for/hasheq ([(k v) (in-dict config)])
+                           (values v k)))
+  (define segments (for/set ([item pattern])
+                     (dict-ref config-reverse item)))
+  (dict-ref segments-table segments))
+
+(define (output-value config strs)
+  (map (λ (pat) (decode-number config pat)) (map (compose1 list->set string->symbols) strs)))
+
+(define (rec->output rec)
+  (for/sum ([digit (reverse (output-value (wire-config (first rec)) (second rec)))]
+            [power (in-naturals)])
+    (* digit (expt 10 power))))
+
+(check-equal? (apply + (map rec->output recs)) 986179)
\ No newline at end of file
diff --git a/2021/08.rktd b/2021/08.rktd
new file mode 100644
index 0000000..ce56799
--- /dev/null
+++ b/2021/08.rktd
@@ -0,0 +1,200 @@
+fgcae ebafc cabdef eg abecfg abgfed feg gafdc bceg ebgcadf | defagbc faecg cfdag gecb
+eagd cad fgadbc aefdcg dcebfg fcegd cbeaf ad dbgfeca defca | cfdeg gdcabf fcgde afgced
+gfdeca aeb eb fbdag eafdc adfbe cefdab bdaegcf efbc ecadgb | eb dbafe eab faecd
+facbdge efdg gcafd daegc caegb aecfdb ade ed gafbdc dgfeac | de abcdef faedcg dfgca
+dcaegbf bc dcgeab cbgad cebg cdfaeb fbadg acdge cefdga cdb | gdcfae gbec gdace cgadfe
+ceagfbd fbaeg fadge fbegad abgecf dafcg ed edab ged dfcbeg | gebfa de gbafec ed
+acedbf adfbg cgafedb geac cgb befcgd bcgaf bfgace cg bfeac | bcdfeg fecba cafgeb bgdfa
+egadc cea ac agbcedf cgab bgcade fbcaed eadfbg fegdc ebdag | fdecabg fcged cdbage efgdab
+cbfge gdc cdea efdag dc cdfeg gfbcad gcdeaf cdeagbf egfadb | dfcge egcfd fcdbag dc
+gaedb fbced gcdbef cge gc decgb dcbgfea cgfb cgdfea fbcade | fdegbac fecbd ecg degba
+geaf bcfedg agbcd bfeagd dgfbe cbdaef beacdfg abe agebd ea | fbecdg geaf gebfad adgbc
+bed afgebd adecf bafgedc dbca cfegb becdf fabdce bd gcfdea | gfdaeb ebfgad dbefc cbda
+gacfebd ag bedfca agbfde egfcab dfga degab fbade bag bdecg | dgaf abcfed agb bfecag
+afebg afdeg gcbe acebdf cfbage cafeb gab decgabf bg gcfdba | gb caebf abgef acfebd
+efdab fabdgce gcbfa eg gacbfe beg ecag beafg dfabcg bgecfd | bge fgdcbe gcfdba ebdaf
+aecbd bdagef gd bfega aefgcbd gfde gfdcab dbg edgba febagc | dg dagfbc dgfe eabdgf
+gdfba egfacbd gdcefa baf gcba fdagcb dgfac ab dcfeba ebgdf | dcfag bfa gafcd cbag
+afbe bdagc cedfb defcab ebfdgac gfedbc cbfad af adgcfe adf | dafbc dfbac fdcegb gadcb
+fcgedb ca fdcage cagdbef ceab acedfb fdbce cafdb cda afgbd | ac dcafb efgdac ebcfda
+fbad gbcda dcefgb cfeadg dgbcaf bcafdeg ad gcabe adc dfbcg | gbcdef bcfdg cgbfd bfadgc
+afcgeb bedag bdecafg agb bedfga fdagce bg bgfd dfgea cdabe | badge cagdfe efdag afegbd
+gfed dcaef ge bafdce daceg acebfg cefadg egc ecdabfg gacdb | bcgad bcegaf agecd degcafb
+deacb adcge ab acb fbdce faedbgc fgadec gabd deabgc ecbfag | dfbec ab cbagfe bcfgae
+gcabfde ecf cbdeg bacgf fedg ecfgb gfedcb fcaedb cebdag fe | dbcegf bcgdfe gfde defg
+daefb bfg gedafb fabge dbafec cfega bdga cgbdfe gb gbacedf | aecfg bcedaf begdcf dgba
+bagce bf bdacfeg efbg fcb cefab gbfadc cafebg ecdfa bacdge | fegb cegba bagce efbg
+becag cfeg cefgbad fbace gfeacb acdegb bef ef adbcf fdabge | ef bdfac cbegad gbeac
+egb afcbe fbaeg eabgfdc gcab gb gfdea fgbecd bcdafe gafbec | fcdgeb edcgbfa gbe fgeba
+dga caebd ecdag cegfd abdfce dafbge ecbgda bcdgefa ga agbc | afdbec ecfdab gdaec gad
+fc gbdefc cfe ebdaf fcbeda gbafde edacg bfcdgae dacef cabf | decgfba cdbefg cf ecdabf
+febgd dafgbc caed cgd ceadgf fbecga dcgfe aegfc gbedfca cd | dgfeb fgced dcafebg agdfce
+ecdafgb bgade bgd fabd gbaef bd egadbf ceadg cfbgea dgbfec | edagc bdage bfda dbgae
+cgeba aefgcd dfceagb dc ced facbed cdfb dbaec adfeb fgedba | fbdea bgcae efbda fcdeag
+caegbf dcfga afcedgb afgdcb fcedag ab edbcg dbfa gdcab abg | bag cbdag agb ab
+gadfecb befc fgdbea cf fedagc fac bcgfa agbfe adgcb feagcb | gbcda cgbad bcgfa cf
+dae aefcb dgabec dacfg afebdc ebfd afecgb aedcf fbcagde ed | ecabfgd bedf bcadef egdacfb
+abcf fcega fdgce fegbda eafdcgb ac gabecd gbfae beagfc eca | edbgca edbfga cae gface
+bgedcf afcdbg ag gcbaef fcedgab afgdb cfgbd befda acdg agf | fdbga ceadbfg egfbac fag
+bad edafc bdeg abcgde ecafgbd gfadcb bgaec db edcba geafcb | cdafe fdcabg cdfageb dbge
+geb bgcf agfcde gb befag gfbcae defab gabdec eacfg gabecfd | afbedgc gceabf abgef egacf
+fdeac acg cfegda cbeadf fegdbca ag acefg adge bfdgca gbcfe | gecdaf efgca cgbafd cfgeb
+begdf bdfgc ebcf adfcg cdegbf dgeafb cbg cb bfeagdc gbdcea | acgedb fagdbe bgfde dfgac
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+bdeafg acgebdf dgcfa fa cafe dgfbc gaf edagfc cgabde agedc | fadbge bdgfcea dgcefa cgeda
+gacfbde defag cbgef gbca efadcb afcbeg cgbdfe ba eba gefab | fegab abe ebfcgd fbgae
+gfbdec fbcade cabdegf ebdg bfd dcfgb cadgf gebcf db fcabge | eacdgfb bdge ebdg ecafdb
+egcfba fdcae fcdaeb gcfdae fabd ba cdeab fcdbaeg eba decbg | cabed facbed cbade dfcea
+agdfe acfdeg fcdbeg dgf gdaec df cadf ceagbfd abgfe gbdaec | bgcdef abfge gbefcd df
+dgebf afgdb bfa fcbade af dcafgb agcf gcbda dabgecf gadecb | dbcga abcdge fadgbce eagcbd
+dbcga bea egacdf dageb be efbd abgfce gadfe fcbegad aebfdg | eba be bdage bedga
+gcbd egbdafc fgc fbgedc gc aedbfg cefgb fedbg cfaegd efabc | bface egfbc bgdacfe gc
+fdgae dc ced gbcd gbcefd decfba becfg ecfabg cgfde gbcadfe | edbcfg cd cafgbe cdegbf
+geadcf efg gadef fg fecad acbgfe dagecbf dcgf gadbe afbdce | edafcg bgcfade gfdc abedg
+edcba ecgdb aedbcf aebf dabfc fdacge badgfc ae ead gfcbade | gcebdaf degbc ebfadc efdcba
+caedbg dbgec dcbf ecgdbf cgdef dgf bgaedcf egacf afebgd fd | cdfbeg ecfbgda gcbfed cbgedf
+bdag acdeb ecgdb egbcfa fcdbega gb dbecag cbdafe ebg gdcef | bedgc abdfcge efagcb cdgef
+bfade bfdga dfbgec cagbfd dfgacbe gba gacf ag gdcbf abgedc | cfag abdcge ebafd abefd
+agcdef bcfda bdgca aebdfcg eagdc gb dbg gbea cedagb bfgdec | dfabgec eafdgc acdge gdecab
+ebacdfg cgbfad egdbc bdgfa daef bae gabed febadg ae gacbef | fagdb daebgf fgdab bea
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+edgfbca gbe be ceba bdaecg gefcd dbagc egbadf dcegb dfgabc | gcfde gfceabd gfbcad eagfdb
+dfcbg fcdga efgb gecbfd gecbda dfbgaec bedfc dgb bfadce bg | dbcgf bfge dacgf dfgcbe
+cga ebdgaf bfdag cbgfe bfadgc gbfeadc ac cagfb cdba cgadef | bfdag agedcf aegcbfd gcfab
+gcead gfdbec cbdge gabfce eb dfgcba ecfdgab befd dgcbf ebg | cdgae fbdegc bcdge gcdfb
+da ebgfda fcdeagb acgbfe gedba dbegc agdecf dae bafeg bfda | gdafec fegba edfbga aed
+fbagec gdfba bcg gebcfd cbafg bcdfgea ebac cefag faedcg bc | gfbac baegcfd fabegc dgeacbf
+dfbeag fabdg fdbe abdeg eb dcega gcefba cfdbag dgcfbae geb | cgbafd bdef dcage eb
+abdcfe gba dagf cagbefd fdbea bfega ag dafbge dcbeag gfceb | afbcde ecgfb dfbega bdgeca
+dg dge gdbc cfdae bcgae cbdage abgfde cfedagb cdgae eacgbf | eabgc bgeac bcdg cagbe
+bfd dgaeb gcabde fd bfgce dgfa dbefg gadbfce dbafge fabcde | edfcba efbcg df bdf
+gcbfd agbecd fedc edcbfg fdb eadfbg bcfag fd gedcb gbacdef | fgbac bdagfec gfbdaec aegbdc
+cgbdfe ce acedg adcfeg bcfegad fcea ceg abdeg afbdcg fcgda | ecg aefdcg dacge ec
+egbdfca efacb agcdbe cbaed bdafgc dfaecg debg bd bda agced | geadbc efbca gabfdc bd
+edcfb bfgecd ecabfd eca abcd fgeab fedcag abfedgc ac bfeca | bgfae eca cdgfeb bfaec
+cadef cebdga ebd bacdfe dagfec dbfa fcebg ecbgfad db fdecb | befcd acgdeb abdf dbfa
+gbfecda bfd cdagb fbdacg fgdbec gbaf cbadf aefdc eadcgb bf | adcgb dfbca agbf dafcb
+abedg acbgf fd gaefcb cagbdef cdaf dcbfeg bdagf dgcbfa bfd | gbadcef df fadgb gabcdf
+fbgadc dbcfg dcega cgdfe cfedbg caefgb ef gef gfaebcd fedb | fcedg febd gbcdfa cdgfab
+bg adgb fcaedbg cgfda fcbae bcg dfacge fgcdba decgfb bcagf | cgafb dbfcage bdgcfe dbga
+ed afbdg acefb aecbfg cfdabeg gedfcb fcdabe ecda def ebdfa | gbafd gedfcb dfegcb dfgba
+gcdfae efgdb abdfcg fde gdabf dbcegfa fedgab efab ef ebdcg | eafb gbfda gacedf cbdge
+edagfc gfaecbd bgced cbegfd cb gefdc badgfc bdc efbc adegb | dgbec cegafd dcbgef dgecb
+gedcab beg eg cafgb fbegc gdfe bdgfec gabcedf bdafce bcdfe | gcefb afcbed ge gdfe
+fdbagc cdgefab edacf ceba ea cfbaed ecfdg abfegd adfbc eda | ea beadfc abcgdef ecdgf
+fbc gfbacd fecda cbdfa dbgf dceabg gbcdfea efbgac cdabg bf | gbdf agbced gaedbc gfdb
+aegcb bfgecd fbegad fcagdbe dfgce fcbd gdeacf fb bgf bgfce | bgafedc gcdaef dgfcbe eadgcf
+def dbce agdfeb ed fdgbcea dgcfb aegfc dfgbac gecfd cdfgbe | cdfegb ed cdgfaeb ebdc
+ecbfad afdb eagbfc caebgdf edfcb dgfec cgdbae bd bcafe bdc | bfacegd fbdcae dbc bgfdcea
+dfgba eg cfbead gde bfedgc dceab cabfdge gdbae aecg aedgcb | egd adebg gde debcfa
+cadfb egfb afgbc adbegc ecgadf ecagb fga ecfgab bgacfde fg | afcbg cgfba gf dacbge
+cegbf dec efcdg facdge dfae dcbafge ed adgfc fdbagc cgaebd | dce gbcfe afcdgbe dcgabf
+cfabe fa eabgfc cgaf fba gfbce dcfbge edbgcfa efbadg acebd | cfebga bfa fedcagb abfce
+acdfb dbagf afcebgd beag afgedb gfdea gbd fgdcbe gb cdeagf | dafge gafed gfacde gb
+gdfeac dfgce ebfadcg edagc dacf baegdc fd gdf egcfb dabgef | degfbac cfdeg daebgf cdeagb
+fcgabe ebcd ecfdg dabcgf gfecabd cfd ebcfg dc bcfegd adefg | agedf cd bcefg dc
+cbaeg bcfea fb feb gfaceb gdfbec dagbec gfab deacf bgcaedf | acbfge bf afgb efb
+egdba cadgfbe efadbg cg begc bfgdca caegd abcegd dcg acdfe | fbegcad bceg gcd cdgebaf
+agbcd dafcgb cfdg ceadb fdgeba eafbcg gfdab gbc bgdcafe cg | gfadcbe fbagd decba gc
+gfbec adgc dge egdcfa abgfde abgdfce dg eacfdb fdaec gdfce | fecgd gd fgcbe acdef
+fdbceg bfedc af fegcad cbdag daf efab dabcef fbeadgc cbfad | fcabd cbfad gcfdbe gadbc
+ebgac fabdeg bedca cg aegdcfb geacbf ceg efgba facg fbedcg | gecdfb aebfg fagc ceg
+eagb dcgeb ba abd cbeagd cdgafb fecbdga fgedcb dacfe dacbe | bdfeacg cadgbf bgedfc fcdae
+dbac cfgae cbfgde ba bga gcfbad dcfebga gcdbf feagbd cgbaf | cgafb fagbdc dcfbg afgebd
+adbgfe fgb egdafc cbafd dfegbc edgafbc egfcd cegb gfcdb gb | bg fdacge efcadg egdfba
+agfbe cgaefdb gbdf edagb afg cdgafe gfedab fg egcdba fabec | fcbdega fag agf agf
+cae edabfc cdfega ca cfba gadeb fdecb ecagfbd cbgdef acdeb | facdeb fgecad bfadce efcgbad
+facb dbfec dceabf efgcd cb aecfbgd dgfbae eafdb ebdagc bcd | bfedc cdegab cbdfe adefb
+fecbga badgc dga bfgadec dg geacb cgedba dfebag gcde fcabd | decg gda baceg gd
+gecbd gcbdfea cbfg bg bge egbcdf dcbef beafdc cdeag bfgeda | agcde dceag gfabde beg
+gefba gacfbe facdeg cg cgab gfc efbdcag cfgeb cefbd afegbd | gfc afbge dafegb aebcgf
+egd aebfgd gefc ge gedbfca bdcfe dfcegb gecdb edbacf cdbag | dacbg edcfbg bcdfe ge
+df ebdga gcdefa cfbd bgdfa afgcb dfeagbc bfacgd fgd facebg | gaebd gecbaf fdcb dfbag
+fag cegfdab cadebg dabcgf abefg eafc ecafgb ebacg fbdge fa | ebfag dbcgfae gbecad fdbgac
+gecbd gefa gfc fabdcg bfaecd ecgafbd fg befgc efabc gecbfa | gfae gcf egbdafc edgbc
+bfgae fcebag fdbe fd fedag adgfbc fdbgea ecagd agcbfed fad | fgabe dfeb ebfd gefba
+ecdgfb afge bdage ebcda eg abdgef fgadb gabcfd dge bcdagef | gdebfa eg agfbdec afeg
+dbc acefd cegadbf fbcde afcb fdcaeg bc acdbge febdac debfg | ceafd caefd gfbaced dcb
+fecgb fgacd gdcefba de gbafce febd gecfd edc fecdbg ecbgda | becdfg ed becgad gcdeba
+agfdbe fbac bcd edacfb bgecfd cb cdeba cfgdeab acged edfab | cb dbc adbce bdfae
+dgacef bdfa ecgbf ab fegba dgafe efdbgca abg acebdg afbdge | gefda ecgafd ecfbg begcad
+gbfcea bgfa afdebc aegdcb af bgcdfea bgeac gecdf afc fgace | bfgecad fca afc abfg
+cfe dgcfe fdagcb gebdc egfa gbcdefa dcebfa fe agdfc fgaedc | dfgac fe fce fcdbega
+fecgab gcbdef cbaefgd dfgbe dgcfe eb bfe dbfga edbc acfegd | fbdeg fdgeca agefbc egcfd
+aecd bac dfacbe cafdb ac gefcab gfcdbe fcbde gbdaf cbdegaf | gcdbefa fbgcae ecad fagecb
+eagbf cagedf geafdbc fdgbce adefb aecfd adcb deb faecbd bd | ebd deabf fadcge cdagfe
+gadefcb bfcga eadcgb egdbfc deag ecg edabc acedbf eg abgce | gdea bagce gce gce
+agcfe bec gecab gbeda facb dbfgec fcegab gfacde gfdaceb cb | cb cefdgb cadefgb bc
+fdgb df egabcf fegda cedga fegab efdbac def cgdefba gafedb | facdbe bafceg agedf fdebga
+fdaecg dbcafg abfgec dc caefg cedg aecfd abdgfce eadbf fcd | cgefab gbfacd fbegac fabecg
+dfecabg bcfeag gdafce dagbfc cdefb dca gafbc dbag da bcadf | dca bagfce cbfda cdagbf
+dabfgec febadg gbcdae gfbe adebf ef cabdf edfgca ebgda eaf | gfacbed abgced egdfca egfb
+cfdea dc fdagebc fegcbd agdc gcfade fcabe cfd efdgba gfead | bdfcge agdc dgefa cfd
+gbfca febadcg bc bdegcf beca begaf gabedf cgfbae cgfad cbg | bcg dcaefgb dfgceb afebdg
+cg cgbf bedcg fcagde adefbcg efdgcb ebacd cgd edbfg egdafb | cfgedb bgcf acegdf cfgb
+bfad adcgbe faceg fagbdc df afdgc efcbdag dfbegc gfd badcg | gfd abgcd fgd abfd
+bcadgf cgdfb adgcb gf gafc dcfeabg bdagce dgf dfbega cebdf | adcbfg gfca fdcbe gfac
+daebf fcabgde bgdcef gab ga edbcga afcg ebfga aefbgc egbcf | ebcfg ebcgfa fcgebd agcf
+gedab fg afgecb cfgd feg cfabed befdc fgdcbe gdceafb befgd | ecafbg ecfbd febdc gf
+gcbadf ce gfcdb fec feabd gbecdf dbcfage febdc agcdfe egbc | bafed gcbe gefcbd egcb
+cbdfg gbcafd feb gaecf gcbfe gfbdae be fcgabde bdgcef becd | abgedf gdfebc aedgfb fbe
+edacgbf fbdae edgac bg gab bagdec dagfce fadbgc cebg bgdea | aedgb bg cebg adcge
+bda gbfea gedcab gfbceda bgdfa bfcdg febcdg bagcfd cfad da | dbecag bgfdc gdbfa facd
+ceabd dabfe acgde bc fbca cgbfde febgda dfecagb ebafdc bdc | cbdae dbfea fgdceb gbfedc
+acg fadbgce cfgdeb dbgce efdca ag dbga cagbef egacd cdgbea | gdecabf gcbfea ecbdg gac
+dfgacb ged egfdab efcgbda gcefbd debga ebadc ge aegf gfdab | cdfgab cdafgb bfcgda ge
+gdbeca bcfde eafg cefbgad dgafcb ge degfb adefbg dgfba bge | bdfeg begdf ebfadg eabdfgc
+cfbdgae gbaec bagfcd gfcba dcaeg bacfeg dbeacf bec efgb eb | ceb egcab cagfb dgcae
+fdcagb gdaecb fcadg bcdgaef gd dfcea gbcaf aecgfb cgd dgbf | gfadc gfdb badgfc gbfca
+bcafed defgcab fgcb cfbae cagde agebfc gbcae gbe gadefb gb | bg gfcaeb bg aedgc
+bcfadeg gbfd eacfbd gdafe afebg bafegd geafcd gebca fb bfa | agdefc eafbdg fgead gedaf
+fcgeabd dgeaf ebgfad gceafb geadc ac aec ebcdg cafd adgefc | gbfadec egcbd acfd dgabef
+eac fbdgec ea eadb cbaeg agfdecb eafdgc dcgbe bcfga adcbeg | aec abde eac ea
+cedb gcadbe ed edgfbac fbega abdge gacdb fdacgb dcefag aed | cdagb gbcafd gdefac gedafc
+cae agfbec ae begcd feab fadgbc ecfadg ecabg cdgbefa cabfg | ecgba afcgb efba dgeafc
+fecgabd badf efadg abedfg fea fdgceb fedgb aebfgc af gdcae | ebfgca fae fea af
+bgedac gbfae dcbefg acbf fb gaedf cagedbf aebgc gebfca fgb | aedgf fdgea bgfae bfdgeac
+bagcfe eadcb gb facegdb bgc fdcag efbcad beadgc bgadc ebgd | gbc fbcage becad gbfcae
+cagde gbca dcgbea gc efcad dbgfea dfgecb caedbfg adgbe cdg | gc egdfbc bcga cg
+efgcbd aebgcd dfe eadfb abged abdcefg bacfd ef bdfaeg faeg | fgae cgdaeb adefb afcbd
+cgbfea gcbda gefdcb eadf febag bdf fd febgad fadbegc bgadf | gebcfd fgdbea dfb dbf
+dg cdgfe gecfad dfbce bgefda fgd eafcg efcbag dgac bcdagfe | afdebg gfd aecgf gfcea
+edfga cgefda gcdbe fbae ab egdabf cfgbda deabg bad adefcgb | ebadg agdeb fbae gbdae
+gbdcfa gbade ebgac ecbfa adfgbec badecf bgc gcef fbgace gc | gc fcge gacefdb ebgca
+acefgd ebgaf egfda egcd bgfaecd dgcfa ed abcefd efd abdgcf | def ebgaf fed befcda
+fecag cag cfagbd agfcbde fabec eabg fdcge cgbfea fadebc ag | cfgbda dfgbeca efdcg dfgcaeb
+bgecfda ecdag dgfcbe bdgac adbgf afgdbe bfac gdcabf cbd bc | bc acbgefd fagcdb fcba
+ba efacg cfbgde cfdbg bacgf bgfdea abf bcad cfbeadg bgcfad | bcdgef fdgaeb ab cagfe
+cbdaf bafdgc eacbd fd dcf fcabg bcdfeg bedgcfa dgfa agbecf | dfga bgfac df agdf
+edcabf cadbf bgfdcea bgcfad bgcde dfg fg bdfgc cgadfe abfg | adfecg gfbcd acgdfeb cbgdaf
+badgfc dg bagcde bceda dbcfea beafg debag adg fcbadeg edgc | gebda dcagbf dceba egfab
+edcf dacfbg dbcefag fbd df bdegfc ebdagc bgfea begcd bfedg | dgebc cbgde dgfbac bdf
+bdcfg acegfb acebfd fdcag egadcf da daf cgeaf edag bafcegd | gdcaf fgaec bafdec fdaecb
+cagefd fde gdfba fcgaedb abefd ef dafbeg ebfg afcbgd ebdca | egdbfa bceda dfabg bdace
+fcgb gcdae bg gfadeb cbfegd fcabed bdg gcdbe fdcbe adbefcg | dgb gfbdec befdc gfbc
+fabde bgfde bgecda cedgb gf cabfdeg ebfdgc fgbeac fcdg gfb | fgbde efdgb edgbc afedb
+ebacf cedfab fde eabfd fd baecgf bagde agdebfc dfcb egfadc | ebfdgac acdegf abdefc ebfad
+gdcb cd cfgae cgbedf fbegd efgdc fadcbe gfeacdb dce dfagbe | gbcd cde gacfe gefdbc
+geb afedgb bfegca bgade eg dgef gadbc eafdb afebdcg fcbead | cagbd defcba dbafec geafcb
+fgbdc gbfade gba gefa dbafg cbadge bfgecda ga edbafc dfabe | afbdeg dgfba bgdfa dcfgb
+agef badce ef febad cabfdg gdfab cbgeafd egfbdc defgba fbe | abefd geaf gafdbe ebcad
+gd gad bfdg gecba fedabcg fcgeda aedfbc adebf agbdfe dgeab | ebcdaf agd gcfbdae egacb
+cedbfa ba cgbfa abf dfegac cafeg gabe befgca ebdfcag cbfdg | fab aegcf faecbd fdcebga
+daefg febdga aegfdbc efgdca eafb bge eb agbdec febgd gbdfc | gbcfd edbfg egb bacegd
+fbdecg bdafec cfaeb gedac def dceaf abfd fd gfecba gfdaecb | ebfac bdfa gbcdef fd
+fcbga cbdfeag bafgce fdacg dc fcd fcgbad fadge efcdgb cdab | gaefcb bafegcd acdb abcgf
+ecgabd acgdf abge ae bcfead fgdaceb ead daegc bcdefg gcbed | egba gaecd cgadbe gdbce
+aegfbc gf afebdc agebdfc ebcdf feg dcefg bdfg dcgea bgedcf | edbfcg fdgb bdgafce febgcd
+dcg bcdefa dbfceg fdeacg acbeg bfeagcd cfdae dg dfag agdec | dfcgea dg egdca edagc
+agcfeb fagbed fdbceg bag gebfd afgd agbfcde acbed ag badeg | cbdea fcedgb gfebac abcegf
+adbegfc fgdace cadge afcg ebdfca ebgad eac bfgdce cgefd ca | acged fcedg ebagd dgacefb
+gfeadb gfeab bcfa agebcfd aebgfc fecgbd efc fc gadec egcfa | fgbace fc debgcf afgceb
+bacg ab cfgbd bfadge acfed fgdecb agedcbf fcabgd bfa dbafc | gfdcb cbga abcg afecbdg
+ge beagc cfgabd bgaced bgcda fbadgec age ecdagf egbd fcbae | aeg gedbac cadfeg fbgcda
+dgbafe abfdgec gdf fd agebcf gadec dfcgba befd edfga aebfg | abcgefd dagec dfg df
+edfcga bcegd baeg cbgdae agdbc gce acgdebf eg gfadbc cefbd | dcbeg bgedc cedbg edcbg
+adfbe dg cagef dfgb gdbeca aefdg gda edcbaf fdgeba gdecbfa | cdabef eafbd bafcegd dg
+cd edcbfg dbage fcaebdg facd bgcfea afbedc afbec dbc adecb | adegb bcefag abegd cbgedf
+gdcbf da ecgbfda adc adgb bagcfd dfbcea egfac dfbceg gdacf | gdba cfdbg adbfec fcaeg
+bcg bc gdcbae dbca abfgde gdeba ebfacdg egcba faceg dgfbce | geadb badecg ecbfgd baecg
diff --git a/2021/09.rkt b/2021/09.rkt
new file mode 100644
index 0000000..b6899a0
--- /dev/null
+++ b/2021/09.rkt
@@ -0,0 +1,36 @@
+#lang br
+(require racket/file rackunit)
+
+(define depths
+  (for*/hasheqv ([(line lidx) (in-indexed (file->lines "09.rktd"))]
+                 [(depth cidx) (in-indexed line)])
+    (values (make-rectangular cidx lidx) (string->number (string depth)))))
+
+(define (neighbors loc)
+  (for*/list ([delta '(1 -1)]
+              [ifactor '(1 +i)])
+    (+ loc (* delta ifactor))))
+
+(define (low? loc)
+  (< (hash-ref depths loc)
+     (apply min (filter-map (λ (li) (hash-ref depths li #f)) (neighbors loc)))))
+
+(define low-locs (for/list ([(loc depth) (in-hash depths)]
+                            #:when (low? loc))
+                   loc))
+
+(check-equal? (apply + (map (λ (lp) (add1 (hash-ref depths lp))) low-locs)) 539)
+
+(define (higher-adjacent loc)
+  (for/list ([neighbor (neighbors loc)]
+             #:when (and
+                     (hash-has-key? depths neighbor)
+                     (not (= (hash-ref depths neighbor) 9))
+                     (< (hash-ref depths loc) (hash-ref depths neighbor))))
+    neighbor))
+
+(define (basin-at loc)
+  (remove-duplicates (cons loc (append-map basin-at (higher-adjacent loc)))))
+
+(define basin-sizes (map length (map basin-at low-locs)))
+(check-equal? (apply * (take (sort basin-sizes >) 3)) 736920)
\ No newline at end of file
diff --git a/2021/09.rktd b/2021/09.rktd
new file mode 100644
index 0000000..1ed5ac3
--- /dev/null
+++ b/2021/09.rktd
@@ -0,0 +1,100 @@
+9976786789439313678999989767678999865435679398654323678999987654313468954569865334568916987643236789
+9754395678998754599898978954567999976556789498775413478998798743203457893479973212479425698432145799
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diff --git a/2021/10.rkt b/2021/10.rkt
new file mode 100644
index 0000000..8399ec8
--- /dev/null
+++ b/2021/10.rkt
@@ -0,0 +1,43 @@
+#lang br
+(require racket/file rackunit)
+
+(define lines (map string->list (file->lines "10.rktd")))
+(define left-toks (list #\[ #\( #\{ #\<))
+(define right-toks (list #\] #\) #\} #\>))
+(define duos (map list left-toks right-toks))
+(define (matched-pair? left right) (member (list left right) duos))
+
+(define (parse tokens)
+  (with-handlers ([char? values])
+    (let loop ([tokens tokens][lefts null])
+      (cond
+        [(empty? tokens) lefts]
+        [(memv (car tokens) left-toks)
+         (loop (cdr tokens) (cons (car tokens) lefts))]
+        [(and (pair? lefts) (matched-pair? (car lefts) (car tokens)))
+         (loop (cdr tokens) (cdr lefts))]
+        [else (raise (car tokens))]))))
+
+(define (corrupt? parsed-line)
+  (case parsed-line
+    [(#\)) 3]
+    [(#\]) 57]
+    [(#\}) 1197]
+    [(#\>) 25137]
+    [else #f]))
+
+(check-equal? (apply + (filter-map corrupt? (map parse lines))) 366027)
+
+(define (autocomplete-score parsed-line)
+  (for/fold ([total 0])
+            ([c parsed-line])
+    (+ (* total 5) (case c
+                     [(#\() 1]
+                     [(#\[) 2]
+                     [(#\{) 3]
+                     [(#\<) 4]))))
+
+(define autocomplete-scores
+  (map autocomplete-score (filter-not corrupt? (map parse lines))))
+
+(check-equal? (list-ref (sort autocomplete-scores >) (floor (/ (length autocomplete-scores) 2))) 1118645287)
\ No newline at end of file
diff --git a/2021/10.rktd b/2021/10.rktd
new file mode 100644
index 0000000..e842910
--- /dev/null
+++ b/2021/10.rktd
@@ -0,0 +1,102 @@
+{([[[(<<[{[[[[(){}][()]][({}())]]]<{((<>[]){[]<>})({()()}(<>[]))}<{{{}()}{[]()}}>>})[<(<[[<><>][{}{
+([(<(((<[({{({(){}}<{}()>)((<>{})[{}<>})}}[{[(<>())[[]]]{{[][]}(<><>)}}{<<{}()>([]())>([<>][{}])}])](<[{[
+{{[[<[<(<<<{((<>[])([]<>))(<{}><()[]>)}[(((){}){<>[]})<{(){}}<<>[]>>]>{[{{<>{}}<()<>>}<<<>[]>([]<>)>][
+<[{<(({([[([({{}[]}{<><>})<<[]{}>>]<<<{}{}>((){})><{{}()}<{}[]>>>)](([<([]{})<{}<>>>(<[][]>{()()})
+{{<(([<[[{<{({{}<>}({}()))<[<>[]](<>[])>}><[(((){})){[()]<<>[]>}][{{<><>}(<>{})}<<()[]>({}())>]>}<[{[(()<>)
+[<{{{({{[<([<{<><>}{<>{}}><<[][]>[{}<>]>]({<[]{}>[[]{}]}{([]())([][])})){<{[[][]]([]())}>([[[
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+{(<{<({{([[{<({})[()()]><[{}<>][{}[]]>}<<<[]{}>[<>()]>({{}{}}[{}[]])>]<({[[][]]({}())}[(()[]](<
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+[[([[({{{[[(<<()()>[<>[]]>)<[<<>{}>]([[]()][(){}])>]<(<{()<>}[[][]]>(([]{})[[]()]))[<({}[])
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+({[[{<{{<<([(<[]<>>{<>{}})<{()[]}(<>())>])<[{[<><>]({}{})}][<({}())><{()<>}(<>())>]>>>{{(([
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+[[<[<{({[({{([()<>]<()()>)}[<<[]()>>]}((({()()})(<{}>[<>()]))[(({}{}){[]}>(([][])<()()>)]))[{<[<[
+[<<([((<<(([[({}{})((){})]<({}[])[{}{}]>]<{{<><>}<[]>}>)[<{{<>()}<()()>}{<<>{}>[[]()]}>[(([][])
+{(<(<[[((<([{<[][]><()>}[[<>{}]]]<<((){}){[]())>[<()<>>(<>[])]>)<{<[[]][<>{}]>({<><>}[<>()])}({{{
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+<[{[[{[({{{([<()()><<>[]>])([([]{})(<>())]{([]<>){()[]}})}<{({{}<>}{[]})([()()])}<[[[]<>><<>{}>]<[()()]<(){}
+<<[<[{{({(({(<[]()>({}{}))([{}[]][[]()])}{{(()[]){<><>}}([<><>]{{}})})[{[[{}{}]({}())]{<<>{}
+{{{[[[[[<(<<{(()[]){()<>}}<<(){}>(()())>>({(()[])}<<[][]>[<>()]>)>)[{[<(<>())>{<(){}>[{}{}]}]
+(([<[[{(([([<<<>{}>((){})>[({}{})<()<>>]]([((){})({}())]])[[{[()()][()[]]}([[][]](<>()))][<{()<
+([<{{[[{<{[({<()[]>{[]<>}}([()<>]<[]()>))]}>{[<({({}{})})>{{<[<>{}][()<>]>({[]}{[]<>})}{<[[]{}](<>())
+[{<<<{{((<{<<{[]()}<<>{}>>{((){}}{()()}}>}{[((()<>){<>})]({{()()}{(){}}}(<<>()>))}><[<{<{}><(
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+({[<({<{<(<({([]<>){{}[]}}<({}{})[{}{}]>){{([]<>){(){}}}(<[]<>>{<><>})}><[[(<>())]{([]<>)}
+{{[[[<{<(<{[(({}[])({}{}))<<()<>>>][<[{}{}]{()[]}>(<[]<>>{<><>})]}<{[<<>()>]<([]())<<>()>>}>>)
+(({{{<(([[<(<((){})><[[]{}][{}()]>)<{[{}{}]}<(<>[])>>>]])({{{<[<()<>>{()<>}]>([<<>{}>(()())]<<<>{}>{[]}
+{{[[[[({<{[{<[()<>]<<><>>>({<>()}<<>{}>)}(({[]<>}([]))<<<><>>[[]<>]>)]<(<<()()>([]<>>>{({}{}){()()}})[[[<><
+[<<{[[([(<{[{{[]()}{[][]}}{{[]()}{(){}}}]{{[{}<>]([]<>)}(<{}()><<>()>)}}<[<{{}<>}<[]<>>><[[]{}]([]{})>][{({
+[[[<<(({(<<((<{}<>><(){}>)<([]<>)(()[])>)[((<>())<(){}>){{(){}}{<>[]}}]><<({(){}}{{}<>})>{[<[]{}><[]{}>](<()
+({({{<[<<<[{{<{}[]>[(){}]}{(<>[]){{}}}}]{[[{[][]}{[]<>}]{(())([]{})}](<({}{})(()())><{<>()}>)}>>>]([({
+<[(((<{<{[<{{{[]<>}{<><>}}{([][])[<>()]}][[[()<>]<{}[]>](({}<>)<[]()>)]>][(<{{{}[]}((){})}{{<>{}}({}()
+{<{[({<<(<[<([<>]<[]()>)<({}()){()[]}>>([{()[]}[{}{}]])]>(([{[[]<>][[]<>]}[[<>()]<<>()>]>(((()[]){<>{}}){
+<(({<{[(<([(<{[]{}}{[]()}>){{(<><>){[][]}}[{{}()}<[][]>]}])>(<{{{[()<>][()<>]}({{}[]}[[]{}])}}(<{{[]{}
+{<[<[{{<<<([[[{}[]]{<>[]}](<<>[]>[()()])][(([]<>)]])>([[<{()}{<><>}>[(<>[])<{}()>]]]{<{<[]{}>[[]
+([{[[<<<<{<[({[]{}}(<>()))[<{}<>>[[]{}]]](([{}<>]){{[]()}[<>[]]})>[{(([][])[{}[]]){(<><>)(<>[])}}(<{()<>}
+<<(([<{[((<[(<(){}>[<><>])[<<>[]><()())]]{<{()[]}(()<>)>}>)[<<{<(){}><{}()>}{[{}<>]<(){}>}>><[<{<>[]}{[][
+(<<[<{<(<<({<([]{}){[][]}>{<[][]>{<>{}}}}[(([]())<<><>>){<{}><<>[]>}])(<{[<>[]]}>{<[{}<>}{<>{}}><{<><>}{()[
+[[[[{<[{[<(<[(()())<{}[]>][(()())<()>]><{{()()}[<>{}]}[({}()><[]<>>]>)<{{[[]<>]<[][]>}{[<><>]
+{{<(({{<{(<([<[][]>(()[])])<<{<><>}<[]<>>><(<>{})>>><{[[[]{}]{<>[]}](<<>{}>(<>[]))}[[<()<>><()<>>]<{()<
+<[({<[[[(<{[(<{}()><(){}>)(<[][]><<>{}>)]<<{{}[]}<{}()>>[(<>())<<><>>]>>{<[([]{})[(){}]]{[(
+[{<<<({<[[[<{{<>{}}<()<>>}{[[]()][(){}]}>{(({}[])<[]{}>){<()>(()[])}}]<{<({}<>)<{}[]>>[<{}{}><<><>
+{<<[(<<<(<[<<{<><>}>({<>()}(()[]))>[([<><>][[]{}])(([]<>))]]>)>[({[<([[][]]({}))<((){}){[]<>}]>[[
+([<{<(<<{({<{<(){}>({}<>)}}{<[{}()][()<>]>{<[]<>>{<>[]}}}}<({[{}{}](<>[])}(<[][]>[{}<>]))<
+{([<<<<{[<<[[<{}{}><[][]>]<{{}()}[()[]]>]<[(()[]){<>[]}][[[]()][()<>>]>>(<[{<>()}(<><>)]{<<>{}>{
+[[([(([[[<[((<()()>)([[]{}]<[]()>))]><{{[[[]{}]([]{})][(()<>)<{}<>>]}([{()<>}]{[<>()][{}[]]})}
+<<{<[<<<({{(<<[]>([])>{<{}<>><<><>>}){<<()<>><()<>>><(<>[])<{}<>>}}}{([{[]<>}{<>{}}](<()()>[{}{}]))<{<[]>
+[{{(([{[<{<{{<<><>><{}[]>}}{<(<>{}){[]}>[([]{})[[]{}]]}>(({[{}]<()[]>}))}><<[{(<{}[]><[][]>)
+[[[<[<[{{[<[{([]())[()[]]}{<{}<>>[()[]]}]<<{[][]}<()[]>>(<{}<>>{[]{}})>>{<<<{}()>><([]<>)[<>()]>>{{(
+{{{([{({[((((([][])[[]()])[(<><>)[()[]]])[[[<>[]]{{}<>}]<[{}[]]([][])>]){[[[[][]]<()<>>](<{}<>><{}{}>
+<<<[({{(<((<<{{}()]<()>>(<(){}><<>{}>)>(<{<>()}<[][]>><{<><>}{[]()}>))[(<([][])[<><>]>(<()()>{{}
+<[(([[(([[({[[[]()]{()()}](<<>{}>)}){<{{<>[]}{{}{}}}{<[]()>[{}{}]}][(<()[]>[<>[]])((<>{}))]}]{[<<<<>
+({{[{<[{([[({[(){}]}[{[]{}}<(){}>])<<({})[[]()]>>]<(({(){}}<[]>)<[<>{}}(<>())>)>])}<<<<[[[[]<>][{}()]]
+{{{[[([<{({{{<(){}><{}()>}([()()]<<>[]>)}<<[<>()]{{}<>}><<<><>>>>})([(<(()[])({}<>)>([{}<>](<>[]))){(<<>>
+<([([[<{{({{[[<>[]]({}[])]}(<({}())><[<>{}]>)}{[(<{}[]>(<>[]))([[]{}]{[]})]({([][])(<>())})}
+[({({{[{<{{(([{}]){<{}[]>([][])})({[[][]]<<>[]>}[<()<>><[]>])}<<<<{}{}>{[]()}>({[][]}[()()])>({([][])[<>{}]}[
+({<{(<([<[{<{<<>[]>({}{}>}([()<>]<[]<>>)>({{(){}}<<><>>}[({}{})])}]><<[(<<<>{}>([]())>)[[<[]<>>(
+<[{<{<<<({[([({}<>){()()}][<()()>(<><>)]){<{()[]}<<>[]>>{{{}()}[<>[]]}}](((<[]()>{<>()})(({}<>)([]{})))({(
+<<{<[[[<[<[[({()()}({}[]))[<()()>[()<>]]]]>][{[<<({}<>)[[][]]>{{{}[]}<()[]>)>]<{{[()[]][[]()]}}{<[
+<{<{({({[{<{[{()<>}]<<<><>><[]<>>>}[{<[]><(){}>}<{[]{}}(()<>)>]><{<{{}()}{(){}}>{<()<>>{[]()}}}((([]<>)<<>
+{(({[([(((<<([()()]<<>[]>)[<<>()>(<>{})]>[<<<><>><()>>]>[((<()()>((){})))[[<()<>><()()>)({{}[]}
+<[<[<{<[{[[([[()()]<{}<>>]){[[{}[]][<>()]]{[[]{}][()<>]}}]]<[{((<>())[[][]]>}([[()<>]<[][]>])](({[
+((<<[[{<({[([{<><>}[<>{}]]){(([]{}){(){}})}](<({{}()}<()<>>)({[]()}[[][]))>{{{{}()}[[][]]}<(<>{}){<>[]}>}
+<{{{[([({{[(<<[]<>>[{}<>]><<[]{}>(())>)<[[<>{}]<{}<>>]<{()}<{}{}>>>]}{{[<(<>{})<[]()>><[(){}]>][{([]())}[<
+[{<[<(<<{({[[<[]<>><()()>]([()()]<<>{}>)]}{(<{[]()}([]<>)><{()[]}>){<<[]()><{}<>>>({()}<<>[]>)}})}{
+[{(({[{[{(<[(<[]{}>(<><>))]<[{()}({}())]>><<[({}[]){<><>}](<[][]>[()[]])>[[([][])([]<>)](([]{}])]>)}]<[<[
+<({[([(<(((({(<>())<{}[]>}[(<>[]){()[]}]))){[([([]{})(<>()]]([()()][{}<>]))<<{{}}(<>[])>{{()
+((({{({<{<({[(<>[]){()()}]([{}[]][{}{}])})(<<{[]{}}>{<[]<>>{()[]}}>)><{{{{{}()}}{[{}[]]<<>[]>}
+(<[<<[([[{<[<({}()){()}>(<(){}><<><>>)]>{{([()[]]<<>()>)(<[]<>>)}{[{<>[]}[<>()]](<<>()><()[]
+((<<({<((<(<({<><>}({}<>))({{}{}}(<>()))>((([]()){(){}})[(()())(()())]>)>){{<([{<>()}(<><>)]<{<>()
+(({(<[({({([<{[]()}<<>()>>{(()<>)[[]()]}]{{[()()]((){})}{[{}<>]{(){}}}})}<<<(<()()>[{}{}])<([]{}){{}[]
+{({[[{([[[<((<(){}>{{}()})[(<>{})])([[<>[]]<()[]>][(()())<[]{}>]>>]((({[{}<>]<{}{}>})({<{}[]>}{(<>
+[[(({<<{[(<<(([][]){{}<>}){[{}[]]({}[])}>(({<><>})<(()<>)[<>()]})>{({[[]{}]((){})}[([]())])})(({([[][]]
+<[<{[<<<{[{(<[<>[]]>{{(){}}[[]()]})}[<{[{}{}]}><(<{}()]{{}{}}){({}[])}>]]}>[({{(<({}[])({}<>)>[{{}<>}])}{
\ No newline at end of file
diff --git a/2021/11.rkt b/2021/11.rkt
new file mode 100644
index 0000000..7fcc973
--- /dev/null
+++ b/2021/11.rkt
@@ -0,0 +1,52 @@
+#lang br
+(require racket/file rackunit)
+
+(define (make-octopodes)
+  (define octopodes (make-hasheqv))
+  (for* ([(line lidx) (in-indexed (file->lines "11.rktd"))]
+         [(depth cidx) (in-indexed line)])
+    (hash-set! octopodes (make-rectangular cidx lidx) (string->number (string depth))))
+  octopodes)
+
+(define octopodes (make-octopodes))
+
+(define (neighbors loc)
+  (remove loc
+          (for*/list ([rd '(-1 0 1)]
+                      [id '(-1 0 1)])
+            (+ loc (make-rectangular rd id)))))
+
+(define (increment! loc)
+  (cond
+    [(number? (hash-ref octopodes loc #false))
+     (define next-val
+       (match (modulo (add1 (hash-ref octopodes loc)) 10)
+         [0 'flashed]
+         [val val]))
+     (hash-set! octopodes loc next-val)
+     (when (eq? next-val 'flashed)
+       (for-each increment! (neighbors loc)))]))
+
+(define (find-flashes-and-reset)
+  (for/list ([(loc val) (in-hash octopodes)]
+             #:when (eq? val 'flashed))
+    (hash-set! octopodes loc 0)
+    loc))
+
+(define (part-1)
+  (for/fold ([flashes null]
+             #:result (length flashes))
+            ([step (in-range 100)])
+    (for-each increment! (hash-keys octopodes))
+    (append (find-flashes-and-reset) flashes)))
+
+(check-equal? (part-1) 1705)
+
+(set! octopodes (make-octopodes))
+
+(define (part-2)
+  (for/or ([step (in-naturals)])
+    (for-each increment! (hash-keys octopodes))
+    (and (= (length (find-flashes-and-reset)) (length (hash-keys octopodes))) (add1 step))))
+
+(check-equal? (part-2) 265)
diff --git a/2021/11.rktd b/2021/11.rktd
new file mode 100644
index 0000000..3b26fea
--- /dev/null
+++ b/2021/11.rktd
@@ -0,0 +1,10 @@
+3113284886
+2851876144
+2774664484
+6715112578
+7146272153
+6256656367
+3148666245
+3857446528
+7322422833
+8152175168
\ No newline at end of file
diff --git a/2021/12.rkt b/2021/12.rkt
new file mode 100644
index 0000000..9d34427
--- /dev/null
+++ b/2021/12.rkt
@@ -0,0 +1,38 @@
+#lang br
+(require racket/file sugar rackunit racket/set racket/bool)
+
+(define links (for/set ([line (file->lines "12.rktd")])
+                (list->set (string-split line "-"))))
+
+(define (is-downcase? loc) (equal? (string-downcase loc) loc))
+
+(define (paths-from last-loc links [small-caves (set)])
+  (match last-loc
+    ["end" '(("end"))]
+    [loc #:when (and small-caves (set-member? small-caves loc))
+     (define pruned-links
+       (for*/set ([previous-locs (in-value (set-remove small-caves loc))]
+                  [link links]
+                  #:when (set-empty? (set-intersect link previous-locs)))
+         link))
+     (paths-from last-loc pruned-links #false)]
+    [loc
+     (define next-lc-visited (cond
+                               [(false? small-caves) #false]
+                               [(and (is-downcase? loc) (not (equal? loc "start")))
+                                (set-add small-caves loc)]
+                               [else small-caves]))
+     (define links-with-loc (for/set ([link links]
+                                      #:when (set-member? link loc))
+                              link))
+     (define remaining-links (if (or (equal? loc "start")
+                                     (and (is-downcase? loc) (not small-caves)))
+                                 (set-subtract links links-with-loc)
+                                 links))
+     (for*/list ([link links-with-loc]
+                 [next-loc (in-value (set-first (set-remove link loc)))]
+                 [path (paths-from next-loc remaining-links  next-lc-visited)])
+       (cons loc path))]))
+
+(check-equal? (length (paths-from "start" links #f)) 5576)
+(check-equal? (length (paths-from "start" links)) 152837)
\ No newline at end of file
diff --git a/2021/12.rktd b/2021/12.rktd
new file mode 100644
index 0000000..6a77547
--- /dev/null
+++ b/2021/12.rktd
@@ -0,0 +1,23 @@
+QR-da
+QR-end
+QR-al
+start-op
+zh-iw
+zh-start
+da-PF
+op-bj
+iw-QR
+end-HR
+bj-PF
+da-LY
+op-PF
+bj-iw
+end-da
+bj-zh
+HR-iw
+zh-op
+zh-PF
+HR-bj
+start-PF
+HR-da
+QR-bj
diff --git a/2021/13.rkt b/2021/13.rkt
new file mode 100644
index 0000000..be77b0d
--- /dev/null
+++ b/2021/13.rkt
@@ -0,0 +1,40 @@
+#lang br
+(require racket/file sugar rackunit racket/set)
+
+(define-values (point-strs fold-strs) (splitf-at (file->lines "13.rktd") non-empty-string?))
+
+(define points
+  (for/seteqv ([str point-strs])
+    (apply make-rectangular (map string->number (string-split (string-replace str "," " "))))))
+
+(define creases
+  (for/list ([str fold-strs]
+             #:when (non-empty-string? str))
+    (match (string-split str "=")
+      [(list "fold along y" numstr) (* +i (string->number numstr))]
+      [(list "fold along x" numstr) (string->number numstr)])))
+
+(define (do-crease points [stop-at +inf.0])
+  (for/fold ([points points])
+            ([crease creases]
+             [i (in-range stop-at)])
+    (for/seteqv ([pt points])
+      (define imag-diff (- (imag-part pt) (imag-part crease)))
+      (define real-diff (- (real-part pt) (real-part crease)))
+      (cond
+        [(and (zero? (real-part crease)) (positive? imag-diff))
+         (+ (real-part pt) (* +i (- (imag-part crease) imag-diff)))]
+        [(and (zero? (imag-part crease)) (positive? real-diff))
+         (+ (- (real-part crease) real-diff) (* +i (imag-part pt)))]
+        [else pt]))))
+
+(check-equal? (set-count (do-crease points 1)) 706)
+
+(define matrix (do-crease points))
+(for-each displayln
+          (map string-join
+               (for/list ([row (add1 (apply max (map imag-part (set->list matrix))))])
+                 (for/list ([col (add1 (apply max (map real-part (set->list matrix))))])
+                   (if (set-member? matrix (make-rectangular col row)) "X" " ")))))
+;; draws word LRFJBJEH
+
diff --git a/2021/13.rktd b/2021/13.rktd
new file mode 100644
index 0000000..188121b
--- /dev/null
+++ b/2021/13.rktd
@@ -0,0 +1,865 @@
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+
+fold along x=655
+fold along y=447
+fold along x=327
+fold along y=223
+fold along x=163
+fold along y=111
+fold along x=81
+fold along y=55
+fold along x=40
+fold along y=27
+fold along y=13
+fold along y=6
diff --git a/2021/14.rkt b/2021/14.rkt
new file mode 100644
index 0000000..fbb8bf6
--- /dev/null
+++ b/2021/14.rkt
@@ -0,0 +1,54 @@
+#lang br
+(require racket/file sugar rackunit racket/dict)
+
+(define lines (file->lines "14.rktd"))
+
+(define (template->duos template-str)
+  (define cs (string->list template-str))
+  (for/list ([c1 cs]
+             [c2 (cdr cs)])
+            (list c1 c2)))
+
+(define starting-template (car lines))
+(define template (frequency-hash (template->duos starting-template)))
+
+(define rule-strs (cddr lines))
+(define procs (for/list ([rule-str rule-strs])
+                        (match-define (list pat repl) (string-split rule-str " -> "))
+                        (define duo (string->list pat))
+                        (define replc (string-ref repl 0))
+                        (λ (h)
+                          (match (hash-ref h duo #f)
+                            [#false null]
+                            [duo-count
+                             (define new-left-duo (list (first duo) replc))
+                             (define new-right-duo (list replc (second duo)))
+                             (cons
+                              (cons duo (- duo-count))
+                              (map (λ (new-duo) (cons new-duo duo-count))
+                                   (list new-left-duo new-right-duo)))]))))
+
+(define (do-insertion template steps)
+  (for/fold ([template template])
+            ([step steps])
+    (define delta-dict (append-map (λ (proc) (proc template)) procs))
+    (define this-template (make-hash))
+    (for ([(k v) (in-dict (append (hash->list template) delta-dict))])
+         (hash-update! this-template k (λ (val) (+ val v)) 0))
+    this-template))
+
+(define (element-counts template)
+  (define orig-template-cs (string->list starting-template))
+  (define h (make-hash))
+  (for* ([(k v) (in-dict template)]
+         [c k])
+        (hash-update! h c (λ (val) (+ val v)) 0))
+  (for-each (λ (c) (hash-update! h c add1)) (list (first orig-template-cs) (last orig-template-cs)))
+  (for/hash ([(k v) (in-hash h)])
+            (values k (/ v 2))))
+  
+(define (score template)
+  (- (apply max (hash-values template)) (apply min (hash-values template))))
+
+(check-equal? (score (element-counts (do-insertion template 10))) 2703)
+(check-equal? (score (element-counts (do-insertion template 40))) 2984946368465)
\ No newline at end of file
diff --git a/2021/14.rktd b/2021/14.rktd
new file mode 100644
index 0000000..eb79acf
--- /dev/null
+++ b/2021/14.rktd
@@ -0,0 +1,102 @@
+BVBNBVPOKVFHBVCSHCFO
+
+SO -> V
+PB -> P
+HV -> N
+VF -> O
+KS -> F
+BB -> C
+SH -> H
+SB -> C
+FS -> F
+PV -> F
+BC -> K
+SF -> S
+NO -> O
+SK -> C
+PO -> N
+VK -> F
+FC -> C
+VV -> S
+SV -> S
+HH -> K
+FH -> K
+HN -> O
+NP -> F
+PK -> N
+VO -> K
+NC -> C
+KP -> B
+CS -> C
+KO -> F
+BK -> N
+OO -> N
+CF -> H
+KN -> C
+BV -> S
+OK -> O
+CN -> F
+OP -> O
+VP -> N
+OC -> P
+NH -> C
+VN -> S
+VC -> B
+NF -> H
+FO -> H
+CC -> B
+KB -> N
+CP -> N
+HK -> N
+FB -> H
+BH -> V
+BN -> N
+KC -> F
+CV -> K
+SP -> V
+VS -> P
+KF -> S
+CH -> V
+NS -> N
+HS -> O
+CK -> K
+NB -> O
+OF -> K
+VB -> N
+PS -> B
+KH -> P
+BS -> C
+VH -> C
+KK -> F
+FN -> F
+BP -> B
+HF -> O
+HB -> V
+OV -> H
+NV -> N
+HO -> S
+OS -> H
+SS -> K
+BO -> V
+OB -> K
+HP -> P
+CO -> B
+PP -> K
+HC -> N
+BF -> S
+NK -> S
+ON -> P
+PH -> C
+FV -> H
+CB -> H
+PC -> K
+FF -> P
+PN -> P
+NN -> O
+PF -> F
+SC -> C
+FK -> K
+SN -> K
+KV -> P
+FP -> B
+OH -> F
diff --git a/2021/15.rkt b/2021/15.rkt
new file mode 100644
index 0000000..fb750a0
--- /dev/null
+++ b/2021/15.rkt
@@ -0,0 +1,59 @@
+#lang br
+(require racket/file graph rackunit)
+
+(define lines (file->lines "15.rktd"))
+
+(define grid (for*/list ([(line ridx) (in-indexed lines)]
+                         [(num cidx) (in-indexed (map string->number (regexp-match* #rx"." line)))])
+               (cons (make-rectangular cidx ridx) num)))
+
+(define data (make-hash grid))
+
+(define (row-length data) (add1 (apply max (map imag-part (hash-keys data)))))
+(define (col-length data) (add1 (apply max (map real-part (hash-keys data)))))
+
+(define (make-grid-graph data)
+  (define rows (row-length data))
+  (define cols (col-length data))
+  (define g (weighted-graph/directed null))
+  (for ([k (in-hash-keys data)])
+    (add-vertex! g k))
+  (define (edges-between pt0 pt1)
+    (add-directed-edge! g pt0 pt1 (hash-ref data pt1))
+    (add-directed-edge! g pt1 pt0 (hash-ref data pt0)))
+  (for ([v (in-vertices g)])
+    (unless (= (real-part v) (sub1 cols))
+      (edges-between v (add1 v)))
+    (unless (= (imag-part v) (sub1 rows))
+      (edges-between v (+ +i v))))
+  g)
+
+(define (preds->path preds dest)
+  (for/fold ([path (list dest)])
+            ([i (in-naturals)]
+             #:break (zero? (car path)))
+    (cons (hash-ref preds (car path)) path)))
+
+(define (solve data)
+  (define g (make-grid-graph data))
+  (define-values (paths preds) (dijkstra g 0))
+  (define dest (make-rectangular (sub1 (col-length data)) (sub1 (row-length data))))
+  (hash-ref paths dest))
+(check-equal? (solve data) 487)
+
+(define big-data (make-hash))
+(define rows (row-length data))
+(define cols (col-length data))
+
+(for* ([(k v) (in-hash data)]
+       [rowrepeat 5]
+       [colrepeat 5])
+  (define next-val (+ v colrepeat rowrepeat))
+  (hash-set! big-data (+ k (make-rectangular (+ (* colrepeat cols)) (+ (* rowrepeat rows))))
+             (cond
+                 [(> next-val 9) (- next-val 9)]
+                 [else next-val])))
+
+;; graph library is too slow to solve big grid
+;; needs dynamic programming
+#;(solve big-data)
\ No newline at end of file
diff --git a/2021/15.rktd b/2021/15.rktd
new file mode 100644
index 0000000..3c1904e
--- /dev/null
+++ b/2021/15.rktd
@@ -0,0 +1,100 @@
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