I only have two phases, but to try to make it as polished as possible, this morning I'll finish adding a menu, transitions, cutscenes and music, so I'm screwed
In my experience in game jams, you really have to learn how to prioritize your time, I don't think I've ever made a game for one that didn't have some kind of major feature cut- but that's part of the fun, it's good practice to know how to trim down your estimates as you go.