I'm glad you liked the feedback.
If local multiplayer isn't a thing, as you say, then I also think it would be a great idea to include those gamemodes, maybe after the jam ends. I have a few ideas about how them would work:
- Coop: Same game, but the players cooperate to get as much score as possible before losing their lives (2 lifes for each player instead of 4).
- Versus: Similar to coop, but the game ends when one of the players dies. Maybe to make it more competitive, the players could be able to push each other by crashing their UFOs against the other players. I would play that mode.
You may have other ideas better than mine, but for now that's all I wanted to tell you.
Great work man!