Hey, thanks for playing the demo. Sorry for not replying to you earlier but we did take your notes and work on some bits specifically due to your comments, so thank you :). We've got an updated demo out now!
In the new demo we've improved the controls including variable jumping and implemented coyote jumps. It may be because I've played it countless times now, but it feels a lot less difficult to play. The game can run in windowed by pressing Alt+Enter but we haven't implemented UI for setting this. Also we scrapped the arena, it wasn't very fun, and no installer for this demo just a self-executable (but things like Avast antivirus do give warnings).
A couple things we've kept for now such as the holding to run which we've been brainstorming ideas about an alternative, and the level select hub which we've neglected a bit!