Not bad for a first game, and you've released it is what matters the most.
That said, there is no real incentive to split, it's easier to just stay as close as possible, maybe give bonus points or replenish lives for collecting multiple green cubes at once. Also at some point you're guaranteed to start loosing lives, since you're either too close and movement is too slow to get all the green cubes or too far apart an you can't evade red ones in time, some predefined patterns for cube spawns instead of full randomness could help with that.
Just keep it up and experiment, you will certainly improve, good luck.