At first I thought this game was really fun. But as mentioned, it does get extremely repetitive. It's still a really nice game, but there needs to be more variety - both with the planets and with the pets. Perhaps have different "enemies" on each planet, rather than just missiles and spikes. And each pet should have a special ability that can be upgraded. Also, I noticed some collision detection seems to be off slightly.
Love the game. Unlike some other commentators, I think the aiming system is perfect. I only have 2 suggestions... 1. Make a power meter on the right side of the screen or where the cursor is; 2. Add a couple more upgrades. Other than that, was a great game! Beat it fully with the poison/balanced/green guy, bout halfway with the other two.
F11, CTRL + mouse scroll down