Nice
Great work for your first game! I'm trying to make a game myself like.
Now, the graphics were good, but not Great. 9/10
no sound so basically that doesn't count, If you add music it could be more enjoyable.
movement was ok, a bit dodgy, but hey, at least you got him to move!7/10
Only two problems you need to fix, just try to make it so sonic dies straight away when he falls and when you jump make sure sonic doesn't push the platform in mid air.
All together it was good, but not perfect. Keep up the work.
P.S. where did you find out how to make a game?