One of the three true gamemodes (i.e. not counting the Credits). The hard one. It does not feature any helpful text. Star Plants are rarer, and might be barren. More enemies appear at once, with tougher enemies showing up sooner. Blocks are placed sporadically, with lots of lone blocks floating in the air. The background is blue. Everything else is the same between Expert and Beginner mode.
The final score is the number of metres down the Pit the Protagonist managed to go before his ultimate demise.