I can't be bothered writing a full review. Here's a few bulletpoints.
*When entering a room, will sometimes continue walking without pressing a button.
*I noticed the longer you play the more complicated the levels become. Increase how quickly this happens.
*Don't remove dissapearing platforms when the head of the character touches them.
*The upgrade system is broken. Upgrades time as soon as you enter the upgrade screen, and *sometimes even without the right number of coins.
*Upgrades are way too expensive. Decrease cost of upgrades.
*Remove time upgrade, keep max time at 10s. Otherwise becomes a bit too easy.
*Number of coins in a room should be based on the difficulty of that room.
*When something is used as a barrier it can be stood on. Breaks a few of the levels.
Actually, if you remove the upgrade system entirely and change the rate at which the complexity of the levels increases, you'd have a damn good game.