What is the fine-grained topic of the following text: The players must take control of two bearded dwarves named Bob (1P) and Jim (2P), who are armed with hammers with which to kill the various enemies that populate the game's five worlds (each one is comprised of ten levels, for a total of fifty); every tenth level is also a boss level, and if they manage to collect all the secret keys, they will have to play through five additional worlds, for a chance to see the good ending sequence (the bad one, which shall be seen when the game ends in the usual way after the fiftieth level, just says "OH NO! Only return the topic.
The gameplay and level structure of a dwarf-themed video game.