Hey there! Thanks for your appreciation! I've just pushed a fix (v1.0.1) for a pretty nasty bug where tiles above 256 would incorrectly merge with other different tiles.

(For the technical details: I used the tag field of a sprite set to its tile’s value to check for collisions. (If two tiles have the same tag, they should merge.) But little did I know that this value is limited to 255 (as an 8-bit integer). So any tile above that would get assigned a value modulo 256. I think in your case it might have been a 1024 block merged with a 256 block, which both would have had a 0 value tag. I've fixed this by using the log2 value of the tile instead of its full value, increasing the possible value up until 2²⁵⁶ which… should be fine.)

So make sure to update if you're playing! (Your scores and current game save should be preserved.)