The concept is nothing new, but it was executed decently for the most part. There are a couple of issues I have with this game.
1. The upgrade prices could be lower or the coin and gems values could be higher to make it so upgrades aren't so hard to buy.
2. Big Timmy mode is helpful, but it can also be unhelpful. Since you can't jump while big, there have been a few instances where I'm in Big Timmy mode and when he's reducing back to his normal size, it's right before an obstacle, giving me no time to react, ending my game. This especially pissed me off when I was six points away from beating the high score on the leaderboard . No one who plays this game should have to hope that Big Timmy mode doesn't end right before an obstacle or they're screwed.