Level Up (not the trope) is a platformer in a vaguely similar style to Achievement Unlocked. The Girl has to explore her world and level herself up in order to help The Boy that recently crash landed in her backyard. She can only stay up for so many hours before she has to return home to sleep.The game is available at Newgroundshere.
It's actually The Girl whose past is truly dark and troubled.
Deadpan Snarker: The Girl has some hints of this. For example, when Finger's McGee says that The Girl doesn't want to know how he got his hands on the Dash sneakers, she throws out this gem:
The Girl: Probably because that'd make me an accessory to it.
Elves VS Dwarves: The Squarians versus the Roundites, sort of. There's also a third race, the Hexies, who didn't want to participate in the feud between the other races, and moved as far away from them as possible.
Foreshadowing: The Nightmare levels up too, because she's The Girl's suppressed memories.
Level Drain: This happens at the start of every new day with your levels. Averted with the sleep levels and any skills you have gotten. If you defeat the Nightmare that night, you don't lose your levels.
Fortunately, your levels regain a lot faster than if you'd just started the game on Day One.
Noodle Incident: We never find out exactly how The Boy came to be an amnesiac, but there is one strong possibility: In the flashback at the end, it reveals that The Deity had The Girl's memory erased because she was seeking a power strong enough to destroy him. Presumably, something that powerful actually exists or The Deity wouldn't have bothered trying to keep her away from it. It may be that this power got to him, took him out, and wiped his memories clean.
The Omniscient: Brainy knows everything...including that a player exists who is controlling The Girl's movements:
The Girl: So do I purchase it? Brainy: You make a choice, determined by another's actions.
Orphaned Series: Unfortunately, despite the first game's popularity, and the surprisingly good alpha builds of the second game, the game's creator was unsatisfied with where development was going, and "put it on the back burner" back in 2010.
Tomato in the Mirror: The ending reveals that The Girl is actually a Dark Action Girl obsessed with power. She lost her memories when she tried to defeat the Deity, the most powerful being who had "surpassed levelling". The Nightmare is her subconscious, furious at her failure.