Very addictive game! One major point of feedback: if you ever make it into a full game, make sure you fix the lag that appears to linearly increase with island size. Seems rather odd as there is no actual simulation aspect to this game, other than checking of adjacent tiles when placing a new tile.
So most of the game loop should just be drawing all tiles with their animation.
E.g. when placing a new part of the island, the lag is currently the worst. So that leads me to believe on every island tile placement all tiles are looped or something instead of just the 3x3 of tiles around each of the new island tiles.