Ok so, the game is pretty good overall, the movement mechanic is fun, and the art and sound are fine, but WHY does the game have to be so confusing??? It's based on movement, yet to end the game you have to solve some kind of riddle??? (the description of the game is very enigmatic)
At first you want to collect all the coins, but the timer gets low, so you rush to the right trying to get to the exit but nothing happens (no coin is in sight when you're at the flag so you can't see them change). Then you go back and there's a wall of obstacles, because of course you didn't take all the coins since you rushed. Then you try to only get where the key is (ah, yes, of course, that coin you can't pick up!), not realizing that what's happening is the coins are turning into obstacles at the end. So you end up being trapped again and you need to start another time to clear a path before the end of the timer.
This is way too complicated for a game where the main mechanic is moving precisely.
Either only make the game about getting to the end, or use that "coins turning into obstacles" mechanic, but make it so the player has to get the key at the right, then come back at the left. That way you can put a lot more coin, and the player has to balance getting to the end and getting as much coins as possible to clear a path back.
And even then, just figuring out the controls at the start was too complicated, there should be a clear indication saying "use your mouse", especially when the menu requires you to press enter to start...