An interesting concept, I like it. May I suggest making a sort of 'respawn' time when you crash so that you are able to continue the race without restarting. Obviously more tracks, multiplayer, upgrades (maybe?) etc. would enhance the gameplay.
Good start to a game, 4/5 from me.
I don't get what the problem is with 24, I got it first try in one shot. But yeah, this game is pretty laggy sometimes, and has a couple of bugs like people have mentioned. Sometimes the outcome of your shots seem to be totally random, which is a pain.
I'd say 4/5, potential 5/5 with some improvements.
Pretty good game, you just need to be careful with your ammo. I got the first two achievments and got to tier 8, but I didn't have the patience to get to 21.