The Gray Code Decoder and Gray Code Encoder holes will go live in approximately 7 days. Why not try and solve them ahead of time?
Card Number Validation in all languages in chars. Achievements Cheevos Holes Languages Medals Miscellaneous All Holes 12 Days of Christmas 24 Game 99 Bottles of Beer Abundant Numbers Abundant Numbers (Long) Arabic to Roman Arithmetic Numbers Arrows Ascending Primes ASCII Table Billiards brainfuck Calendar Card Number Validation Catalan Numbers Catalan’s Constant Christmas Trees Collatz Continued Fractions CSS Colors Cubes Day of Week DFA Simulator Diamonds Divisors Emirp Numbers Emirp Numbers (Long) Emojify Evil Numbers Evil Numbers (Long) Factorial Factorisation Farey Sequence Fibonacci Fizz Buzz Foo Fizz Buzz Bar Forsyth–Edwards Notation Fractions Game of Life Gijswijt’s Sequence Happy Numbers Happy Numbers (Long) Hexdump Hilbert Curve Intersection Inventory Sequence ISBN Jacobi Symbol Kaprekar Numbers Kolakoski Constant Kolakoski Sequence Leap Years Levenshtein Distance Leyland Numbers ln 2 Look and Say Lucky Numbers Lucky Tickets Mahjong Mandelbrot Maze Medal Tally Minesweeper Morse Decoder Morse Encoder Multitap Input Musical Chords N Queens Niven Numbers Niven Numbers (Long) Number Spiral Odious Numbers Odious Numbers (Long) Ordinal Numbers PalindromemordnilaP Pangram Grep Partition Numbers Pascal’s Triangle Pernicious Numbers Pernicious Numbers (Long) Poker Polyominoes Prime Numbers Prime Numbers (Long) Proximity Grid QR Decoder Quine Recamán Repeating Decimals Reverse Polish Notation Reversi Rijndael S-box Rock-paper-scissors-Spock-lizard Roman to Arabic ROT13 Rule 110 Scrambled Sort Set Seven Segment SI Units Sierpiński Triangle Smith Numbers Spelling Numbers Star Wars GPT Star Wars Opening Crawl Sudoku Sudoku (Fill-in) Ten-pin Bowling Tic-tac-toe Time Distance Tongue-twisters Topological Sort Tower of Hanoi Transpose Sentence Trinomial Triangle United States Vampire Numbers Van Eck Sequence Zeckendorf Representation Zodiac Signs γ λ π τ φ √2 𝑒 Alphabetic Numbers Apéry’s Constant Binary Lambda Calculus Connect Four Crossword CSS Colors (Inverse) CSS Grid Ellipse Perimeters Flags Floyd-Steinberg Dithering Gray Code Decoder Gray Code Encoder Hexagonal Spiral Highly Composite Numbers NFA Simulator Numbrix Odd Polyomino Tiling p-adic Expansion Polygon Triangulations QR Encoder Quadratic Formula Rectangle Fill Semiprime Numbers Smooth Numbers Snake Sphenic Numbers Taxicab Numbers Turtle Tutorial All Languages ><> ALGOL 68 ArkScript Assembly AWK Bash BASIC Berry brainfuck C C# C++ Civet Clojure COBOL Coconut Common Lisp Crystal D Dart Elixir Erlang F# Factor Forth Fortran Gleam Go GolfScript Groovy Haskell Hexagony J Janet Java JavaScript jq Julia K Kotlin Lua Nim OCaml Pascal Perl PHP PowerShell Prolog Python R Raku Rockstar Ruby Rust Scheme sed SQL Swift Tcl TeX V VimL Wren Zig 05AB1E APL Arturo Befunge BQN CJam CoffeeScript Egel Fennel Harbour Hare Haxe Hush Hy iogii Knight Lily Luau Odin Picat Qore Racket Rebol Rexx Scala Squirrel Stax Uiua Umka Vala Vyxal Bytes Chars Scoring Bytes Chars Language All ><> ALGOL 68 ArkScript Assembly AWK Bash BASIC Berry brainfuck C C# C++ Civet Clojure COBOL Coconut Common Lisp Crystal D Dart Elixir Erlang F# Factor Forth Fortran Gleam Go GolfScript Groovy Haskell Hexagony J Janet Java JavaScript jq Julia K Kotlin Lua Nim OCaml Pascal Perl PHP PowerShell Prolog Python R Raku Rockstar Ruby Rust Scheme sed SQL Swift Tcl TeX V VimL Wren Zig Experimental Language 05AB1E APL Arturo Befunge BQN CJam CoffeeScript Egel Fennel Harbour Hare Haxe Hush Hy iogii Knight Lily Luau Odin Picat Qore Racket Rebol Rexx Scala Squirrel Stax Uiua Umka Vala Vyxal Hole All 12 Days of Christmas 24 Game 99 Bottles of Beer Abundant Numbers Abundant Numbers (Long) Arabic to Roman Arithmetic Numbers Arrows Ascending Primes ASCII Table Billiards brainfuck Calendar Card Number Validation Catalan Numbers Catalan’s Constant Christmas Trees Collatz Continued Fractions CSS Colors Cubes Day of Week DFA Simulator Diamonds Divisors Emirp Numbers Emirp Numbers (Long) Emojify Evil Numbers Evil Numbers (Long) Factorial Factorisation Farey Sequence Fibonacci Fizz Buzz Foo Fizz Buzz Bar Forsyth–Edwards Notation Fractions Game of Life Gijswijt’s Sequence Happy Numbers Happy Numbers (Long) Hexdump Hilbert Curve Intersection Inventory Sequence ISBN Jacobi Symbol Kaprekar Numbers Kolakoski Constant Kolakoski Sequence Leap Years Levenshtein Distance Leyland Numbers ln 2 Look and Say Lucky Numbers Lucky Tickets Mahjong Mandelbrot Maze Medal Tally Minesweeper Morse Decoder Morse Encoder Multitap Input Musical Chords N Queens Niven Numbers Niven Numbers (Long) Number Spiral Odious Numbers Odious Numbers (Long) Ordinal Numbers PalindromemordnilaP Pangram Grep Partition Numbers Pascal’s Triangle Pernicious Numbers Pernicious Numbers (Long) Poker Polyominoes Prime Numbers Prime Numbers (Long) Proximity Grid QR Decoder Quine Recamán Repeating Decimals Reverse Polish Notation Reversi Rijndael S-box Rock-paper-scissors-Spock-lizard Roman to Arabic ROT13 Rule 110 Scrambled Sort Set Seven Segment SI Units Sierpiński Triangle Smith Numbers Spelling Numbers Star Wars GPT Star Wars Opening Crawl Sudoku Sudoku (Fill-in) Ten-pin Bowling Tic-tac-toe Time Distance Tongue-twisters Topological Sort Tower of Hanoi Transpose Sentence Trinomial Triangle United States Vampire Numbers Van Eck Sequence Zeckendorf Representation Zodiac Signs γ λ π τ φ √2 𝑒 Experimental Hole Alphabetic Numbers Apéry’s Constant Binary Lambda Calculus Connect Four Crossword CSS Colors (Inverse) CSS Grid Ellipse Perimeters Flags Floyd-Steinberg Dithering Gray Code Decoder Gray Code Encoder Hexagonal Spiral Highly Composite Numbers NFA Simulator Numbrix Odd Polyomino Tiling p-adic Expansion Polygon Triangulations QR Encoder Quadratic Formula Rectangle Fill Semiprime Numbers Smooth Numbers Snake Sphenic Numbers Taxicab Numbers Turtle Tutorial # Golfer Points Chars Time Submitted 800th voidgloom 425 152 10ms 22 Oct 2024 800th omero-san 425 152 10ms 22 Sep 2025 800th brochmann 🇸🇪 425 152 10ms 12 Oct 2025 804th JOrE20 424 136 1,020ms 7 Dec 2025 805th MeWhenI 🇻🇦 424 143 6ms 2 Oct 2024 806th denisfouchard 422 153 10ms 21 Aug 2025 807th osNiko 🇧🇷 420 154 9ms 21 Aug 2025 808th celiendonze 🇨🇭 417 155 10ms 17 Oct 2025 808th aksyristos 417 155 10ms 15 days ago 810th Arkadios200 417 196 101ms 21 Oct 2025 811th Shotokhan 414 156 10ms 21 Sep 2025 812th lhulinsky 412 157 10ms 21 Oct 2024 813th snoozingnewt 🇨🇦 411 267 29ms 18 Dec 2025 814th ellis-rix 409 158 10ms 9 Dec 2024 815th webmiche 407 159 11ms 3 Nov 2025 816th Mabeloid 🇳🇴 405 159 9ms 12 Oct 2024 817th CheeseCake628 🇳🇴 404 160 104ms 5 Nov 2024 818th snoozingnewt 🇨🇦 404 223 96ms 2 Nov 2025 819th pres-abhisheksinha 401 161 10ms 8 Oct 2024 820th aksyristos 400 172 2ms 23 Nov 2025 821st ibixina 399 162 11ms 13 Oct 2024 821st TheAtrossian 399 162 11ms 5 Jan 2025 823rd Ralac07 🇦🇺 398 162 11ms 3 Oct 2024 824th Maximizer02 396 201 12ms 1 Oct 2024 825th Vaekor 392 165 11ms 15 Dec 2024 826th snoozingnewt 🇨🇦 392 276 40ms 6 Dec 2025 827th dieggsy 389 247 18ms 10 Oct 2024 828th fischfood 385 176 5ms 22 Oct 2024 829th JOrE20 385 191 169ms 27 Jan 2026 830th ehulinsky 🇺🇸 384 158 5ms 2 Apr 2025 831st JesseNoEyes 🇺🇸 382 169 11ms 1 Oct 2024 832nd CheeseCake628 🇳🇴 381 151 521ms 18 Oct 2025 833rd zyc-2024 🇨🇳 380 170 10ms 5 Oct 2024 834th ComputerKWasTaken 🇺🇸 378 171 10ms 14 Oct 2024 835th KatieLG 🇬🇧 375 218 110ms 21 Nov 2025 836th RobGLambert 375 232 1,366ms 8 Jun 2025 837th navier-1 374 173 10ms 22 Sep 2025 838th c0d3-4-F00d 🇩🇪 374 184 2ms 9 Jan 2025 839th RedzGoose 🇦🇺 371 187 114ms 2 Oct 2024 840th P1nk-P0nk 369 215 3ms 18 Oct 2024 841st clayboll99 367 176 10ms 10 Jul 2025 842nd muser-logiccpu 🇺🇦 365 177 18ms 9 Aug 2025 843rd snoozingnewt 🇨🇦 364 313 40ms 2 Nov 2025 844th OSYCh314 🇦🇺 363 178 10ms 2 Nov 2024 845th denkyuu1 361 156 603ms 14 days ago 846th snoozingnewt 🇨🇦 360 267 13ms 2 Nov 2025 847th calum12345 359 180 10ms 26 Mar 2025 848th zt14427 355 182 11ms 27 Dec 2024 849th The-Wolfson 355 230 102ms 16 Dec 2024 850th IoLimmer 353 183 10ms 10 Oct 2024 851st sciencejiho 349 197 2ms 11 Feb 2025 852nd estomagordo 🇳🇱 348 186 10ms 15 Jul 2025 853rd RobGLambert 342 273 200ms 8 Jun 2025 854th Ernest1338 340 275 303ms 26 Oct 2024 855th noahhorlacher 337 191 10ms 7 Dec 2024 856th JOrE20 314 389 56ms 4 Dec 2025 857th snoozingnewt 🇨🇦 303 200 4ms 2 Nov 2025 858th KatieLG 🇬🇧 300 290 2,545ms 1 Oct 2025 859th gautambp 297 218 11ms 24 Jun 2025 860th kasarino 287 240 2ms 8 Feb 2026 861st KatieLG 🇬🇧 286 241 2ms 1 Oct 2025 862nd Zhenyu-Bo 284 228 11ms 30 Jul 2025 863rd fantaize 283 330 198ms 14 days ago 864th EthanJantz 281 230 11ms 5 Sep 2025 865th ReterikHub 280 310 206ms 17 Jan 2025 866th RobertBurs 273 237 10ms 22 Sep 2025 867th Mikey-Beep 🇬🇧 273 349 16ms 12 Aug 2025 868th MeWhenI 🇻🇦 272 407 119ms 6 Oct 2024 869th TJK-S 268 241 11ms 25 Oct 2025 869th NoneTheFewer 268 241 11ms 25 Dec 2025 871st kasarino 258 373 44ms 8 Feb 2026 872nd te-chnical 251 258 219ms 4 May 2025 873rd arebbsba 218 296 11ms 9 Jan 2025 874th kasarino 216 299 11ms 8 Feb 2026 875th Msleizak 🇫🇷 206 226 280ms 19 May 2025 876th benanlam 202 320 10ms 21 Dec 2025 877th theEsteemed 154 606 472ms 20 Jan 2026 878th AidanWalter 120 540 10ms 1 Jan 2025 879th vkptimon 120 776 422ms 9 Jul 2025 880th bignamehyp 97 667 10ms 14 Nov 2024 First Prev 801–880 of 912 Next Last