How To Play

The complete rule

Fill every editable tile with a number from 1 to 5. Equal numbers connected up, down, left, or right form a cluster. Each cluster must contain exactly as many cells as its value: a 2 belongs to a pair of 2s, a 3 to three connected 3s, and so on. Diagonal contact does not connect clusters. Decorative blockers cannot be filled and separate groups.

Matching groups merge when a new tile connects them. Two separate groups of 2s cannot touch orthogonally, because they would become one group of four 2s.

Understand the board's feedback

An expandable, incomplete group stays neutral. A complete group receives a checkmark. A conflict marker identifies an oversized group or one without enough reachable space to reach its number. Selecting a tile shows its size and target.

Feedback evaluates visible cluster rules. A complete cluster can still need to change as you reason about the rest of the board; it is not a secret-answer check.

Solve with fewer guesses

1. Look for constrained edges, corners, and blockers.
2. Find groups that can only expand in one direction.
3. Leave enough space for larger numbers.
4. Check whether placing a number would accidentally merge two matching groups.
5. Use Undo to revisit a decision. Reset Board is also undoable while solving.

Use hints deliberately

A hint fills and locks one tile. The first three per puzzle are free; extra hints cost 40 coins. A hint clears undo history and makes the solve imperfect. Reset Board retains hinted values. Searches that cannot provide a hint spend no coins. Older saved puzzles can have more than one valid solution; hints respect compatible alternative completions.

Daily and Journey

Daily provides a board for each local date, with a rolling archive of the previous 45 days. Use the calendar or date arrows to move between dates. Solved Daily boards stay locked, and reopening them does not repeat rewards.

Journey progresses through larger grids and decorative blockers. A completed board stays visible until you select Next Puzzle. A perfect solve means no hints were used. Consecutive perfect Journey solves can earn milestone bonuses, subject to the daily reward cap. Coin-based streak protection can be offered after a hinted solve.

Saved progress and accessibility

Entries, hints, progress, and coins save locally on the same device. Normal updates retain those records; uninstalling clears local app data. Version 1.1 and later supports optional iCloud sync between devices using the same iCloud account.

VoiceOver reads tile coordinates, values, fixed/editable status, and cluster information. Use its adjustment actions to change an editable value. Larger accessibility text sizes use a scrolling screen with stacked controls. System Reduce Motion replaces moving celebrations with simpler feedback.

Watch actual gameplay · Quick Start · Support

iCloud sync in version 1.1 and later

Enable Settings → iCloud Sync → Enable iCloud Sync on devices signed in to the same iCloud account. No separate ClusterSum account is needed. Enable it first on the device whose coin balance you want to keep: that device establishes the shared wallet. Other devices add their saved puzzles and Daily history without adding their old balances.

Journey progress, puzzle boards, Daily history, themes, and the shared coin wallet sync while ClusterSum is open. Haptics remain specific to each device. Play offline and use free hints as usual; with sync enabled, paid hints and streak protection require an iCloud connection. Earned rewards and purchases are reconciled without duplicate credits.

Use Sync Now to request an update and check the status and last-sync time. If both devices edited an unfinished puzzle independently, alternate saves are retained under Saved Board Versions. Finished boards and Daily completions are kept when saves merge. Local recovery copies are retained when sync is first enabled.