Sumi: Zen Sudoku

墨 Sumi is sudoku, stripped of noise.

No leaderboards. No streaks that shame you. No timers ticking in your face. Just a nine by nine grid, drawn in warm ink on washipaper, waiting for your next move.

FIVE LEVELS OF PRACTICE Five difficulties, from your first quiet solve to the edge of mastery. Each level is a different conversation with the grid.

1. Easy and Medium: unhurried, forgiving.
2. Hard: where focus begins to matter.
3. Master and Edo: for those who have earned stillness.

A DAILY HABIT Open Sumi each day. Solve one puzzle. Watch your streak grow, your times sharpen. The Practice Log tracks your progress with a clean improvement curve. No gamification. Just the graph.

YOUR SEASON, YOUR PALETTE Choose a season at first launch: Spring, Summer, Autumn, or Winter. Each shifts the accent colour that breathes through the interface. Change it anytime in Settings.

SUMI PRO - Unlock the full practice:

1. The Library: a curated collection of passages from Zen masters, philosophers, and makers. One surfaces each day.
2. Design Zen Sudoku: build a print-ready A5 puzzle book. Pick your difficulty mix, your paper colour, your ink. Export as PDF and print.
3. Full improvement history and personal bests at every difficulty.
4. No Ads One-time purchase. No subscription. No renewal.

ABOUT THE NAME 墨 (sumi) is the ink used in traditional Japanese calligraphy and sumi-e painting. Ground from a solid inkstick, mixed with water, applied with patience. The name describes the aesthetic: deliberate, unhurried, lasting.

Ink on paper. No chrome. No noise. Nine by nine, every day.