Glad to hear you enjoyed it. Yea one thing I noticed was that there was a lot of missing feedback initially about what you exactly need to do, different weapons giving more resources, an ever increasing deadline. We didn't really have a lot time remaining to improve this experience so I tried to tackle it with a tutorial overlay that tries to explain the main gimmicks as simple as possible, and some more in game feedback like showing you which weapons are effective. But even with all these changes I think it can still be confusing, since the game immediately starts, giving a new player almost no opportunity to familiarize itself with the systems when they first play. But it's nice to hear you got the gist of it after a few tries.
For the art and SFX style we kept it simple, but like you said I think the main thing is to keep them consistent. I'm quite happy with how it all came together, the shaking and color changing UI, the compressed VFX, it blends pretty well.
I do want to correct that we didn't make the music ourself. Initially we wanted to but we ran out of time so we downloaded it from a royalty free youtube channel. You can find it here or in the description. I get the misunderstanding though since audio is marked as "made by yourself", but we only made the SFX ourselves, not the music.
The ideas you have for improvement align a lot with ours, especially the one about "animations for collecting resources". Initially another system you'd have would be the Space Elevator (I've added an image for the POC where you can see the space elevator) and you would see drones picking up the resources and bringing them here, and would have to balance upgrading your weapons or logistics to improve yield or increase amount of resources gathered. But we had to cut scope to keep time for polishing.
All in all, thanks for the feedback :)