Each level has multiple things to steal/destroy but once you pick up/destroy the first thing, the alarm goes off and a timer starts.

The gameplay is mostly setting up the heist. You break holes in walls, build bridges, set up chain reactions, etc to find a route that picks up everything and escape in time. You have limited ammo but you get unlimited spray paint to mark the path for yourself

I know some people hate it but my only complaint is that some of the DLC is pretty meh. Base game is a blast, though!