Narbacular Drop
Story:
You are Princess No-knees (comically named for her inability to jump), who has been captured by a demon. You are put inside a thingy (forgot what it was), and it's the home of a creature named Wally. Wally is furious with the demon for making the prison inside his home. So, he decides to help No-Knees under one condition: She must help him defeat the demon. He then shows her his portal-making ability, and No-Knees escapes.
The boss fight was never finished, so you get up to that part, and the game ends.
Now you're thinking with Portals.Wait, wrong quote. Whatever.