I'll review the modes separately
Adventure mode:
Gameplay: You click a button and then henry stickmin appears and he doesn't go away, ever, meaning if you click on the button he's just dances like he's the free Minecraft I downloaded from the youtube ad.
Sandbox mode:
Gameplay: It plays like beat the boss, BUT there's no money, assumingly adventure mode would have added money but for now billy is just a punching bag to shoot, stab, explode, and throw! well, that would be if throwing wasn't broken.
Glitches: This game has a handful of bugs, I'll just name them off
B001: Adventure mode sends infinite henry stickmin
B002: Offset pixel in billy sprite breaks throwing
B003?: You need to stop clicking on items for their effect to be applied, this may be a game mechanic and if I'm notified otherwise I'll remove this bug.
TL;DR This game is fun but the bugs soil it, still less buggy than Cyberpunk though
Oh and if you want my review of the art it's the same as my review of Entering the party
Edit: Formating