That's actually quite an interesting idea. I'll be sure to add that to the list. Thanks!
Multiplayer (online) would be quite awesome to set up, and also viable now that I've ditched Flash. However, it wouldn't be a core component of the game, because if the game never gets popular in the first place, then I wouldn't want it to rely on multiplayer.
What's everyone else's thoughts on this idea?
YES.
MORE YES.
ALL THE YES.
That would be the greatest video-gamey-stick-figurey-thing... ever.
You could have purchasable cosmetics and have teams of 4 or something that can group together. You could have each player buy their own items during checkpoints and have a limited amount of time to plan out their strategy of how to work together with the tools they have for the next zone. You could have single player have the option of playing with AI or alone. You could have the option to either fight swarms or various bosses 1 after the other. And/Or, you could have the additional option to fight a swarm with the occasional boss as well. You could even have the option to allow the players to switch between boss only/swarm only/mix with every checkpoint/new zone.
You could EVEN have the option for people to make their own zones in-game and petition them to be added to the list. You could even give players the option to choose and pick their favorite zones and make a custom list that is randomly shuffled every time they play. In Co-Op, you could have the party create their own list or combine all their lists. You could even have different classes/playable characters, maybe even allowing players to design/create their own.
^ Idea stuff, totally-not-a-wall-of-text.