Thanks for the feedback.
We definitely considered creating a small tutorial but ran out of time. Figured it was more important to deliver a finished product, though I solved a few problems by having a begin button at the beginning so that you could kinda mess around without any real threat. My plan for a tutorial was to have each part of the game explained, an enemy that doesn't shoot at you, a pickup to bring back to the ship, how to heal the ship etc.
As for the feedback on hit, definitely should have had some animation/hitflash/damage noise/particle effect. Definitely want to make it feel good to play.
A few other notes: The controls might feel a little loose but I kind of wanted that effect since it's space, but I find that while giving constant inputs it feels pretty good and when letting go it kind of drifts which was neat but maybe not the best experience. I'd considered making the controls super tight which would probably feel ultimately better. I've definitely had that problem of having to refer back to the game page for controls myself, so I'll try to remember that next time.
One last bit is it's pretty obvious that the single player experience suffered due to the multiplayer and we should have made it more additive than reductive, but we would have missed out on the cool interaction between the players and the main ship. Flying the ship, then jumping out to grab loot, and then jumping back into the ship is incredibly difficult for a solo player, especially as the difficulty ramps. And of course the ramping difficulty into infinity is kind of a cop out for real gameplay design but I felt it was fine for this jam.
We also should have added in a credits section, I'm noticing a lot of people did that. The art is from game-icons.net so we can't claim that unfortunately mostly. The music was hand crafted though.