Hey good job getting a game done. I think there were a few simple things you could do to help give the player more interesting choices to make beyond the chaos of initial spawn in. As it stands I got to about 40 by just going in a circle. If you were to randomize the spawn locations of the new balls coming in as well as giving the player some indication where they were going to spawn in, you could force the player into more interesting & challenging situations imo.
Additonally a little more time at the start to understand what was happening or a clue that the arrow keys moved you would have helped. I died about 10 times trying to move the mouse or WASD around before I tried the arrows. Even just posting that on the game page might be helpful.
Good job overall and hope you continue to work on your dev skills!