The physics is definitely in need of tweaking, the bike's momentum works in opposite directions for inclines and declines. All in all, I can see you have potential, but with practice, you'll get better at making these games.
It's an alright start but you could have tweaked it a bit more. The fat guy wants to fall on his back a little too easily. The bike also seems to be powered by two rats running in the wheels because it has like no power. If you lose momentum after a ramp, you can't even get over a small hill with the bike and you must restart. Riding the bike feels a bit too tedious and hard for it to be enjoyable. Could have used more work than just couple of weeks.