The Gray Code Decoder and Gray Code Encoder holes will go live in approximately 29 hours. Why not try and solve them ahead of time?
PalindromemordnilaP 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 391st ryyyn 🇺🇸 718 87 10ms 10 Jun 2025 391st commandz0 🇺🇸 718 87 10ms 11 Jul 2025 391st hiichbindermax 718 87 9ms 19 Aug 2025 391st robin-scragg 718 87 9ms 18 Oct 2025 391st blaztoma 🇱🇹 718 87 10ms 11 Jan 2026 391st Lv0Sys 🇵🇱 718 87 10ms 22 Feb 2026 407th anter69 🇭🇺 717 59 64ms 25 Oct 2024 408th Kacarott 🇦🇺 717 132 3ms 4 Sep 2024 409th KatieLG 🇬🇧 716 99 10ms 5 Oct 2025 410th mykytamatiukha 714 168 221ms 15 Jan 2026 411th snyderek 🇺🇸 712 150 63ms 15 Sep 2024 412th AlephSquirrel 710 88 139ms 1 Sep 2024 412th ahmetdemirag 🇨🇾 710 88 10ms 3 Sep 2024 412th hellwue 710 88 10ms 4 Sep 2024 412th Schreipfelerer 710 88 9ms 11 Sep 2024 412th bob-th 710 88 10ms 17 Sep 2024 412th InigoK 🇺🇸 710 88 10ms 18 Sep 2024 412th moustave 710 88 9ms 24 Oct 2024 412th andrewjc2000 710 88 9ms 10 Mar 2025 412th KasperKivimaeki 🇫🇮 710 88 10ms 19 Feb 2026 421st Shanethegamer 🇺🇸 709 114 104ms 2 Sep 2024 422nd emgordon154 708 85 146ms 1 Sep 2024 423rd alexsave 708 100 10ms 22 Sep 2024 423rd JOrE20 708 100 15ms 21 Feb 2026 425th error256 705 97 15ms 14 Jan 2026 426th adriweb 🇫🇷 704 98 2ms 4 Sep 2024 426th sean-niemann 🇺🇸 704 98 2ms 5 Sep 2024 426th dokutan 704 98 2ms 14 Sep 2024 429th MostParsingVex 703 152 1,832ms 12 days ago 430th CaedenHarper 🇨🇦 703 187 279ms 8 Nov 2025 431st DialFrost 🇸🇬 702 61 973ms 31 Aug 2025 431st Steffan153 🇫🇮 702 61 712ms 17 Feb 2026 433rd OllieBoyne 🇬🇧 702 89 10ms 9 Sep 2024 433rd davecame 702 89 10ms 17 Sep 2024 433rd Bmrl7 702 89 10ms 3 Oct 2024 433rd DialFrost 🇸🇬 702 89 10ms 21 Nov 2024 433rd CommandLeo 🇮🇹 702 89 9ms 27 Nov 2025 433rd ThijsLuttikhuis 702 89 10ms 7 days ago 439th ovs-code 🇩🇪 702 128 2ms 1 Sep 2024 440th CaedenHarper 🇨🇦 701 83 494ms 9 Aug 2025 441st GrayJoKing 🇦🇺 700 86 154ms 2 Sep 2024 441st dokutan 700 86 134ms 15 Jun 2025 443rd snoozingnewt 🇨🇦 699 91 98ms 19 days ago 444th MeWhenI 🇻🇦 698 151 43ms 4 Sep 2024 445th frosster 🇨🇦 697 99 2ms 21 Mar 2025 446th sean-niemann 🇺🇸 697 114 170ms 7 Sep 2024 447th elgan65536 🇺🇸 697 172 209ms 23 Sep 2024 448th mamamia5x 695 102 11ms 12 Sep 2024 449th MeWhenI 🇻🇦 694 59 1,026ms 13 Jun 2025 450th tatzyr 🇯🇵 693 61 37ms 10 Oct 2025 451st stefangimmillaro 693 90 2,686ms 14 Nov 2024 452nd sean-niemann 🇺🇸 692 107 2ms 23 Aug 2025 453rd emgordon154 690 288 1,906ms 2 Oct 2024 454th JDiLenarda 🇫🇷 687 170 1,331ms 3 Sep 2024 455th BlankSpruce 686 91 10ms 1 Sep 2024 455th ZakkkkAttackkkk 🇵🇭 686 91 10ms 1 Sep 2024 455th BREMAUCY 🇫🇷 686 91 10ms 3 Sep 2024 455th charliegaming 686 91 11ms 7 Sep 2024 455th mbittner20 686 91 10ms 9 Sep 2024 455th neihousaigaai 686 91 10ms 28 Sep 2024 455th Rubiksmath 686 91 10ms 1 Oct 2024 455th jameswmccarty 686 91 10ms 2 Dec 2024 455th croc54 686 91 10ms 12 Jan 2025 455th Pyroan 686 91 9ms 24 Feb 2025 455th WillowWispy 686 91 10ms 21 Mar 2025 455th clayboll99 686 91 9ms 15 Jul 2025 455th vhoulbreque 🇫🇷 686 91 10ms 21 Nov 2025 455th FortuiteMan 🇫🇷 686 91 9ms 30 Nov 2025 455th LostSyntax21 🇬🇧 686 91 10ms 30 Nov 2025 455th CaedenHarper 🇨🇦 686 91 30ms 1 Dec 2025 455th solisolu 686 91 10ms 31 Dec 2025 455th mateusz-sterczewski 686 91 10ms 15 Jan 2026 455th Matter1024 🇮🇳 686 91 10ms 31 Jan 2026 455th souta-1326 686 91 11ms 19 Feb 2026 475th GolfingSuccess 🇬🇷 686 131 2ms 1 Sep 2024 476th kaascevich 685 116 2,277ms 15 Sep 2025 477th MeWhenI 🇻🇦 684 88 150ms 1 Sep 2024 477th error256 684 88 154ms 10 Sep 2024 479th DialFrost 🇸🇬 682 62 36ms 30 Jan 2025 479th KatieLG 🇬🇧 682 62 38ms 2 Oct 2025 First Prev 401–480 of 767 Next Last