Appreciate the in depth explanation and each point of feedback, that's exactly what I'm looking for! I know some of the levels at the moment leave much to be desired — they're pretty much all placeholders for now since I haven't implemented the main overworld map which will eventually help coordinate locations and missions more. Soundtrack is also being thrown together slowly, but nothing good enough to include in the game yet.
There is also so much space for various setpieces which are nowhere to be seen.
I'll try to make sure there's more to see in each level. I can't promise a Valve level minute to minute gameplay maximization, but I understand some more variety would be nice, even for ~3 minute levels.
As for worldbuilding and a proper story — I've been putting most of my work into making the actual game fun before I spend months drawing cutscenes and developing a plot as I'd hate for it all to be wasted on something that ultimately turns out to be an annoyance to play. But I agree that without those elements the actual combat sort of feels pointless.
I've beaten all the levels using all the weapons. I loved the inclusion of flying enemies which interact with environment in a completely different way and it makes me wonder if there could be any water only enemies.
I had enemy gunboats planned for the fourth level, but I simply ran out of time to make them. Some water turrets that pop in and out are also planned.
All in all I want to see more and I think you are steering the game in the right direction. I've shared the game to my friends and can't wait for the next update.
Much appreciated, thank you once again for playing and the feedback! I always take note of critical comments and try to improve the game using what was said.