Play Cosmic Merge • Free

Every run gives you exactly three undos, and the button shows how many you have left before greying out at zero. Only moves that actually changed the board can be undone - a move into a wall that shifted nothing costs you nothing.

The count survives a page reload, so refreshing is not a way to top it back up. Starting a new run is what refills it. This matters more than it sounds: the temptation is to burn all three early recovering from small mistakes, which leaves nothing for the position that actually decides the run.

You can also undo out of a finished game. If the board fills and you still have an undo in hand, stepping back one move sometimes reveals a merge you missed, so it is worth checking before accepting the loss.

Eleven named rungs run from Dust up to Black Hole: Dust, Meteor, Asteroid, Comet, Moon, Planet, Gas Giant, Star, Giant Star, Supernova, Black Hole. Each one is worth exactly twice the one below it, so the ladder is the doubling made visible.

The chart tracks your progress rather than just listing the objects. Rungs you have already built stay lit, and the next one up is boxed so you always know what the current target is. It answers the question the board alone does not - how far along you actually are.

Past the Black Hole the ladder keeps going to Quasar and Galaxy, and anything beyond that is simply labelled Universe. Most runs end long before that point.

The single most useful habit is parking your biggest object in one corner and building along the edge beside it. If the largest thing on the board wanders into the middle it splits your space in two and blocks merges on both sides.

The practical version of this is to avoid one of the four directions almost entirely. If your anchor sits bottom-left, stop pressing up. Every press of the direction you are avoiding risks dragging the anchor out of its corner, which is the move that quietly loses most runs.

New objects appear in random empty cells, so a board that is nearly full gives you very little room to recover. Merging early and often to keep cells free is usually better than hoarding matched pairs for later.

Your current board, your score and your remaining undos are all saved in the browser, so closing the tab mid-run and coming back later picks up exactly where you left off.

Your best score persists separately and survives a new run. Clearing your browser data clears both.

There are no levels, unlocks or difficulty settings - every run uses the same rules, and the only thing that changes between them is where the objects happen to appear.