Awesome entry!! having the planets follow their own pre set ellipses was a really unique and cool mechanic for a "tower defense" style game and added a nice amount of depth with timing your shots. one thing that might make a fun addition is targeting the bystander planets/sun purposely (for example, if you shoot the sun it gives you some energy, or if you do enough damage to one of the smaller planets it breaks and the shrapnel can damage the humans). it was fun figuring out each attack and trying to beat the humans. love the art style of both the game and the cutscenes; the aliens actually made me laugh which was cool and the sounds you chose were great. having each attack have a specific method of firing instead of all being the same was a good touch too . one critique is with the UI, when you open the shop it blocks out half of the screen and makes it impossible to see what is happening on the battlefield. and since you spend a lot of time buying items from the shop this becomes an issue.
Overall i really enjoyed this entry with its unique take on tower defense and the funny alien backstory, great job everybody!