A simple little game.
What a great game. A simple little objective of collecting the gold coins while avoiding the red. Very fun.
Upgrades: I don't know why people are asking to put in upgrades. In the stage that it is, it's really not suitable to have upgrades. I would say you would need to add a few more things before thinking of such an idea.
Adding "rounds" to the game would really be an improvment. Just throwing an idea out there: I would put in an objective to collect a certain amount of coins to allow players to move on to the next stage. In doing this the game will be less likely to lose players from the lack of excitment.
If you were to add rounds, I see no reason not to add upgrades. Giving yourself the ability of a magnet pull on coins, another heart, speed, size you name it.
I am not going to go all out on this review, but if you would like to know more, just PM.
The background of the game is a little bland. Well it's just a white screen. But really nothing to be concerned about. A new color for every level would be a pretty fun idea.
About the music. I would suggest putting in a simple beat that doesn't get tiresome. Nothing too big. Probably a simple Techno beat would do it.
I think you have a great game on your hands. With a little work and some time you could make this into something unique.
Keep up the great work, and I look forward to a sequal from you.