Title: Rescue a Princess: A Dungeon World Tale
System: Dungeon World, powered by Apocalypse Engine
Setting: Player-created Unique Dungeon World
Characters: Basic Character classes from Dungeon World, found on the SRD here.
If you have any questions, check out the rules, or ask in the threads or via PM!
Dungeon World Guide: http://www.dungeon-world.com/dungeon-world-guide/
If you aren't sure how Dungeon World will work or feel to play, read this guide. It is a fantastic introduction to the principles and ideas behind playing. Highly recommended.
Dungeon World SRD: http://www.dungeonworldsrd.com/
The rules for DW are Creative Commons - Attribution, so they are freely available online at this SRD. In particular, the Playing the Game section is essential before you start playing, laying out the tone and tenor of the game. If you don't do anything else, read that section and the DW Guide above!