I feel like the mechanics could be better explained; it took me a few tries at the third jump to realise that I should shoot the bubble horizontally. Mark Brown explained that in the Mario games, the mechanics are always first shown in a safe environment where players can test it without consequences for failure - you could've done that for the horizontal bubble and its effects. Apart from that, the game could definitely benefit from more polish - more textures for the ground and environment, better animations, UI that is in front of the tiles and not behind them (it's possible to cover up some of the text by walking to the left at the start) - the usual stuff.