Amazing game! I really like the look, mechanics, and replayability—one of the best I've tried on PICO-8.
After a lot of rounds, my Onslaught high score is 3,710. I think the difficulty is spot on, as it scales well after reaching the last charge.
My only wish is for more abilities, so that they get less repeated during a round.
Also, to add to the experience, perhaps you could unlock Onslaugh after beating Survival, and Nightmare after reaching a certain score on Onslaught. This way, players have something to look for other than getting a high score.
Edit: Additional feedback after playing more.
- After getting the last charge on Onslaught, I'd prefer not to be asked if I want to continue (instead, maybe move that option to the menu). I've ended many games by mistake.
- I wish the Mimic ability didn't copy an ability that it's already copying. For example, if it's copying Split, and I swap with a crew member that also has Split, I wish it chose another ability (if available).
- Is there a way to show the difference between "attacker" enemies? So that we can plan ahead, instead of waiting for them to shoot.