It's a nice game. I agree with Konnie_6 considering having to click reset all the time, and I'd add that having to click adjust and start is also frustrating. Maybe the velocity could be set by the ditance between the canon and the mouse, or the duration of the click (like in worms).
Also, I think that 2 different musics are playing in the first screen (and they don't have the same bpm so it feels weird). Otherwise the music is good and fits with the mood of the game, good choice !