Simple and enjoyable gameplay, with a very cute art style. Excellent work!
It took me a few rounds to figure out how the controls actually worked and the intended mechanics, the instructions could use more detail.
I wonder if you left test values in? I start on either round 5 or round 2?
Sometimes the rockets disappear and never come back, which is a shame as the art is gorgeous.
Unfortunately I find the high score mechanic to be a test of how long you are willing to play rather than a measure of skill or achievement. I could play optimally for 10 minutes and lose high score to some one who plays poorly but played for 10 hours.