I've given that some thought as well. I don't think I have the ability to intuition required to have the mechanics be fun enough to just fiddle with in a kerbal space program kind of way where you just kind of want to tinker with what you can do. I think it will need to be sort of a survival imperative. I put in a heart rate, (or breath rate I haven't decided) toggle that adjusts the speed you can flap (and ideally stamina/health drain). I set it so that at idle the drain is zero, but... you can't flap fast enough to actually fly... I like that a lot. So you try and fly but you can't get it unless you engage with the mechanic. I think choosing a swallow or a swift will help with that a lot. You have to be in flight to eat so... As of now I think survival simulator is probably the right scope. If I can get to the stage where there is a tutorial fledging level, a survival/attract a mate level and a raise a baby bird level that is a complete game, but might be beyond the time limit for a solo beginner like myself. I think maybe food-health-song quality might be the way to go where you need to have built up enough strength to consistently sing a good song to get a mate as a player goal.