About Shikaku Daily
Full guide — rules, scoring, and the history of Shikaku.
The History of Shikaku
Shikaku (四角に切れ, roughly "divide into squares") is a logic puzzle created by Nikoli, the Japanese puzzle publisher responsible for popularising Sudoku and dozens of other pen-and-paper puzzles. Shikaku first appeared in Nikoli's puzzle magazine in the early 1990s and quickly gained a following for its clean premise: simple rules, a deterministic solution reachable by pure logic alone.
Unlike Sudoku — which deals in numbers and rows — Shikaku is fundamentally spatial. You partition a grid using area as the only constraint. A well-constructed Shikaku has exactly one solution, and reaching it requires no guessing, just careful geometric reasoning.
Shikaku Daily generates a fresh, computer-verified puzzle every day across three difficulty sizes — each with a unique seed so no two days are alike. Every puzzle has exactly one solution.
How to Play
Divide the grid into non-overlapping rectangles. Each clue number must be the only number inside its rectangle, and that number must equal the area of the rectangle (width × height). Every cell must belong to exactly one rectangle — no gaps, no overlaps.
- ▸Drag from any cell to another to draw a rectangle. Release to place it.
- ▸Right-click or long-press a filled rectangle to remove it.
- ▸Drawing a new valid rectangle over an existing one replaces it — no need to erase first.
- ▸A rectangle is valid only if it contains exactly one clue number equal to its area. Invalid placements are rejected with a shake — keep trying.
- ▸The puzzle is solved the moment every cell belongs to a valid rectangle.
Tip
Prime numbers (2, 3, 5, 7…) can only form 1×N or N×1 rectangles — start with those to anchor the grid. Large numbers constrain nearby smaller clues and are usually easier to place than they look.
Difficulty
Three difficulty levels are available every day. The puzzle auto-starts on the difficulty seeded for that date; the other two unlock once you complete it.
| Difficulty | Grid size | Points multiplier | Daily chance |
|---|---|---|---|
| 🟢 Easy | 6 × 6 | × 1.0 | 25% |
| 🟡 Medium | 8 × 8 | × 1.5 | 50% |
| 🔴 Hard | 10 × 10 | × 2.0 | 25% |
The difficulty multiplier applies to all trophy tiers — finishing Hard always earns twice the base points of Easy.
Trophies & Points
Points are based on how quickly you solve the puzzle. Each puzzle has three trophy cut-offs — Gold, Silver, Bronze — calculated from the day's seed and difficulty. Thresholds vary ±15% day-to-day so every puzzle feels fresh; today's exact targets are always shown in the puzzle header.
| Trophy | Typical time (Easy / Medium / Hard) | Base points |
|---|---|---|
| 🥇 Gold | < 10s / < 18s / < 28s | 30 pts |
| 🥈 Silver | < 15s / < 27s / < 42s | 20 pts |
| 🥉 Bronze | < 30s / < 54s / < 84s | 15 pts |
| ✓ Completed | Any time | 5 pts |
Final points = base points × difficulty multiplier + streak bonus. Example: Gold on Hard = 30 × 2 = 60 pts, plus any streak bonus.
Streak Bonus
Complete at least one puzzle on consecutive calendar days to build a streak. The bonus applies once per day regardless of how many difficulty levels you play. Miss a day and the streak resets to zero — but your All-Time points are kept.
| Streak length | Bonus points |
|---|---|
| 1–9 days | +5 pts |
| 10–19 days | +10 pts |
| 20–49 days | +15 pts |
| 50–99 days | +20 pts |
| 100+ days | +25 pts |
Example: Gold on Medium (20 × 1.5 = 30 pts) with a 14-day streak (+10 pts) = 40 pts.
Leaderboard
There are three leaderboard views — switch between them with the tabs above the board.
- ▸Today — ranked by total daily points (highest first). Shows all trophies earned across difficulties for the current day.
- ▸30 Days — cumulative points over the last 30 days. Rewards consistency.
- ▸All-Time — cumulative points since you first played. A full historical record.
Only your first completion per difficulty per day earns leaderboard points. You can replay as many times as you like for practice, but only the first submission is recorded.
Your Account
Shikaku Daily requires no login. Your nickname and score history are tied to your browser via a unique identity tokenstored in localStorage. If you clear your browser data or switch devices, you'll need a recovery code to reclaim your account.
To generate a recovery code, open the nickname menu in the header and choose Recovery Code. Codes are 6 characters in the format XXX-XXX. Anyone who has your code can access your account — keep it somewhere safe (notes app, screenshot, written down).
To restore your account on a new device: open the app, choose a nickname, then tap Have a recovery code? Restore your account → at the bottom of the nickname screen and enter your code. Your nickname, points, and streak are instantly restored.
About 601 Labs
Shikaku Daily is built by 601 Labs — a small indie studio creating thoughtful tools and games.
Spotted a bug or have a suggestion? Get in touch →