Koshi: Shikaku PuzzleSplit
the paper.
Every number is the size of its rectangle.
Fill the grid, one rectangle at a time.
Coming soon to the App Store and Google Play.
Free to play. Optional one-time purchase.
See it in motion
Drag a rectangle.
Earn the seal.
Draw each rectangle in one drag, stamp the seal when the grid is done, and climb from kyu to dan. With Koshi Plus, switch inks and revisit past dailies.
Shikaku, the Japanese logic puzzle
One number.
One rectangle.
Divide the grid so each rectangle holds exactly one number, and that number is its area. Every puzzle has one solution, reached by logic alone.
Today’s puzzle, for everyone.
A new puzzle every day, the same for everyone, with a worldwide leaderboard. No account and nothing to type: you get a name like “Quiet Crane 27”.
Practice without end.
Easy, Medium, and Hard boards, made on your device, as many as you like. Undo, Check, and Hint when you need them; a clean solve scores highest.
From 10 kyu to 9 dan.
Every solve earns XP and raises your rank through the kyu and dan of Go. Keep your streak going with a daily reminder and a widget.
Koshi Plus
Every day.
Every ink.
Play every past daily, color the board with five inks, and take on Expert 12 × 14 boards.
One purchase, never a subscription. Today’s puzzle and practice stay free.
Wherever you play
Your streak,
on every device.
Made for iPhone, iPad, and Android phones, tablets, and foldables.
Games, statistics, your streak, and your rank sync with iCloud or Google Play Games.
Requires iOS 26 or iPadOS 26 or later, or Android 14 or later.
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