Some random ideas I had in case you want to develop this further:
Entities (Self explanatory)
Orange - Functions like a regular red, but gives you an extra midair jump.
Cyan - Increases your maximum combo for the round by +1 (up to a maximum if you choose, but I'd think it'd be rare enough you wouldn't need a max)
Black - Gives a lot of points, but decreases your health instead of refilling it.
Point bonuses (Gives you something when you reach a certain point value)
100k - Permanently changes the aiming white line to account for drop, to make it easier to aim.
250k - Permanently gives you an extra midair jump after bouncing off of things.
500k - Gives you one extra life, where upon death you will simply be launched as if you hit a red entity, but lose the extra life.
1M - Permanently increases the spawn of entities, and increases the space within to play.
2M - Doubles your maximum combo from whatever it is at the moment.
Other Suggestions
Cause entities to spawn on the left side of the starting platform maybe?
A username and leaderboards system could be cool, to compare your high score with other peoples.
That's about it, thanks for reading, these are all just random ideas and you obviously don't have to add any of them!