Very impressive to have a working upgrade system on your first game! Love the programmer music LOL.
Gameplay is fun, but it kinda gets a little repetitive after a few runs when grinding for coins, I think you can easily reduce the repetitiveness it by sprinkling a few randomization here and there. Doesn't have to be drastic, just change the placement/appearance of enemies/pebbles/items on each map, I think it will help a lot to increase the replayability.
Great work! Thanks for making this!