Was so focused on getting a high score that I completely forgot to rate this sooner. Here goes:
This game was very enjoyable, had simple and visually appealing art, really good audio design and even support for other languages which was completely unnecessary for a jam but you still did it for the sake of UX maybe? Actually impressive considering the time you had on your hands. Feature-wise I don't think anything is missing. I wish the controls on the character were a little more responsive at the beginning of the runs but when the game gets faster, the controls feel more responsive which is good. You really nailed the arcade feel on that one. The off-camera canon shots didn't bother me as much as the mountain gaps that just one-shot you. I tried to see if I could press space bar even without that gap, see if I could get an exploit. Game did not give it to me. However in the particular situation I show in this image, you can actually press space to jump over the wall, probably because the code just checks if the player's y position is below a gap or something. This configuration happens rarely enough for it to not matter though, and these are things that don't break the game's flow or fun at all. Might be good for you to be aware of those little bugs though for future stuff or if you plan to extend this..