The Gray Code Decoder and Gray Code Encoder holes will go live in approximately 5 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 801st adamnielson42 🇺🇸 425 152 10ms 6 Oct 2024 801st voidgloom 425 152 10ms 22 Oct 2024 801st omero-san 425 152 10ms 22 Sep 2025 801st brochmann 🇸🇪 425 152 10ms 12 Oct 2025 805th JOrE20 424 136 1,020ms 7 Dec 2025 806th MeWhenI 🇻🇦 424 143 6ms 2 Oct 2024 807th denisfouchard 422 153 10ms 21 Aug 2025 808th osNiko 🇧🇷 420 154 9ms 21 Aug 2025 809th celiendonze 🇨🇭 417 155 10ms 17 Oct 2025 809th aksyristos 417 155 10ms 16 days ago 811th Arkadios200 417 196 101ms 21 Oct 2025 812th Shotokhan 414 156 10ms 21 Sep 2025 813th lhulinsky 412 157 10ms 21 Oct 2024 814th snoozingnewt 🇨🇦 411 267 29ms 18 Dec 2025 815th ellis-rix 409 158 10ms 9 Dec 2024 816th webmiche 407 159 11ms 3 Nov 2025 817th Mabeloid 🇳🇴 405 159 16ms 12 Oct 2024 818th CheeseCake628 🇳🇴 404 160 104ms 5 Nov 2024 819th snoozingnewt 🇨🇦 404 223 96ms 2 Nov 2025 820th pres-abhisheksinha 401 161 10ms 8 Oct 2024 821st aksyristos 400 172 2ms 23 Nov 2025 822nd ibixina 399 162 11ms 13 Oct 2024 822nd TheAtrossian 399 162 11ms 5 Jan 2025 824th Ralac07 🇦🇺 398 162 11ms 3 Oct 2024 825th Maximizer02 396 201 12ms 1 Oct 2024 826th Vaekor 392 165 11ms 15 Dec 2024 827th snoozingnewt 🇨🇦 392 276 40ms 6 Dec 2025 828th dieggsy 389 247 18ms 10 Oct 2024 829th fischfood 385 176 5ms 22 Oct 2024 830th JOrE20 385 191 169ms 27 Jan 2026 831st ehulinsky 🇺🇸 384 158 5ms 2 Apr 2025 832nd JesseNoEyes 🇺🇸 382 169 11ms 1 Oct 2024 833rd CheeseCake628 🇳🇴 381 151 521ms 18 Oct 2025 834th zyc-2024 🇨🇳 380 170 10ms 5 Oct 2024 835th ComputerKWasTaken 🇺🇸 378 171 10ms 14 Oct 2024 836th KatieLG 🇬🇧 375 218 110ms 21 Nov 2025 837th RobGLambert 375 232 1,388ms 8 Jun 2025 838th navier-1 374 173 10ms 22 Sep 2025 839th c0d3-4-F00d 🇩🇪 374 184 2ms 9 Jan 2025 840th RedzGoose 🇦🇺 371 187 114ms 2 Oct 2024 841st P1nk-P0nk 369 215 3ms 18 Oct 2024 842nd clayboll99 367 176 10ms 10 Jul 2025 843rd muser-logiccpu 🇺🇦 365 177 18ms 9 Aug 2025 844th snoozingnewt 🇨🇦 364 313 40ms 2 Nov 2025 845th OSYCh314 🇦🇺 363 178 10ms 2 Nov 2024 846th denkyuu1 361 156 603ms 15 days ago 847th snoozingnewt 🇨🇦 360 267 13ms 2 Nov 2025 848th calum12345 359 180 10ms 26 Mar 2025 849th zt14427 355 182 11ms 27 Dec 2024 850th The-Wolfson 355 230 102ms 16 Dec 2024 851st IoLimmer 353 183 10ms 10 Oct 2024 852nd sciencejiho 349 197 2ms 11 Feb 2025 853rd estomagordo 🇳🇱 348 186 10ms 15 Jul 2025 854th RobGLambert 342 273 200ms 8 Jun 2025 855th Ernest1338 340 275 303ms 26 Oct 2024 856th noahhorlacher 337 191 11ms 7 Dec 2024 857th JOrE20 314 389 56ms 4 Dec 2025 858th snoozingnewt 🇨🇦 303 200 4ms 2 Nov 2025 859th KatieLG 🇬🇧 300 290 2,534ms 1 Oct 2025 860th gautambp 297 218 11ms 24 Jun 2025 861st kasarino 287 240 2ms 8 Feb 2026 862nd KatieLG 🇬🇧 286 241 2ms 1 Oct 2025 863rd Zhenyu-Bo 284 228 11ms 30 Jul 2025 864th fantaize 283 330 198ms 15 days ago 865th EthanJantz 281 230 11ms 5 Sep 2025 866th ReterikHub 280 310 209ms 17 Jan 2025 867th RobertBurs 273 237 10ms 22 Sep 2025 868th Mikey-Beep 🇬🇧 273 349 16ms 12 Aug 2025 869th MeWhenI 🇻🇦 272 407 119ms 6 Oct 2024 870th TJK-S 268 241 11ms 25 Oct 2025 870th NoneTheFewer 268 241 11ms 25 Dec 2025 872nd kasarino 258 373 44ms 8 Feb 2026 873rd te-chnical 251 258 219ms 4 May 2025 874th arebbsba 218 296 11ms 9 Jan 2025 875th kasarino 216 299 11ms 8 Feb 2026 876th Msleizak 🇫🇷 206 226 280ms 19 May 2025 877th benanlam 202 320 10ms 21 Dec 2025 878th theEsteemed 154 606 472ms 20 Jan 2026 879th AidanWalter 120 540 10ms 1 Jan 2025 880th vkptimon 120 776 422ms 9 Jul 2025 First Prev 801–880 of 913 Next Last