This is a defend your base game where you control a ship with a giant magnet attached to it. Fly over junk to pick it up and click to drop it. When your magnet is big enough you can pick up enemies and throw them around.
If you click and hold while carrying some junk you will absorb the junk into your ship and upgrade it. Upgraded ships have larger magnets and look bigger and cooler. To use up a whole bunch of junk on the ground click and hold while flying along the ground like you were some crazy vacuum cleaner.
To upgrade and repair your base just drop bits of junk onto it.