Really fun, but sad that aliens make a challenge only at start, then just grind or i miss something)

I like the idea and the game is pretty fun, but there are some important things missing: Most obvious of all: some way to select the upgrade you want (through a menu or even better by clicking on certain areas / buildings on the planet that visually change on upgrading). There were two displays for coins but only one updated, maybe put it more central directly on top of the earth. I would change the coins to friendly spaceships (color coded so you don't shoot the wrong ones) to emphasize how you get stronger with more soldiers/spaceships. Also some sort of mini game for collecting them would be great since there's no way to miss them atm. I like the explosion sound and the heart UI, the controls feels ok and taking away the control over when to shoot is a great way of making this game stand out. Good job for your first Jam game!

Which part is "Stronger together"?

The idea is overall simple and fun. I had fun playing the game. I have no idea how the upgrade system is suppose to be working. But overall a good first jam game. Well done.