A stand-out submission this year. Great work on nailing your concept early and iterating on its core design in a bunch of interesting ways!
The game as a whole feels at once tight and focused while also taking the time to explore different expressions of the game's core gameplay.
It would be nice to have a reference for which powerups are which, and I found the countdown on some missions to be a little confusing since it's counting down something that's present in other levels, not the thing that's unique to that level.
As always, it's great to see submissions with source code.
Shipping the AppImage as a loose file means that it can't have exectuable permissions when downloaded. Your non-AppImage Linux build does have executable permissions, so I'm not going to mark you down on that, bit it's worth keeping in mind for future builds/projects.