Okay, you have a great concept for a game; unfortunately, execution, controls and interface is not well developed and has bugs. Here are the things that bugged me (puns intended):
* The spring doesn't shoot unless you have more than one grid length of compression.
* There is not menu that allow users to go back and attempt a better score per round.
* There is no way for the user to track previous performance to attempt a better score.
* There was no bar available to gauge the amount of energy being stored per shot.
* User is given three different pieces of information, but there is nothing that helps the user understand how those pieces apply to the round.
* User has to wait for the weight to fall back to the spring before they can start the next round.
* Weight shifts side to side slightly as it ascends/descends.
* There is no background music for the game (not technically required, but always contributes to the game).
I find value in the sketch style that you use to create the game and in the concept of the game. I feel that it needs a more user friendly interface. Just my opinion. Good Luck.