There are 28 different levels in the game and each level has three different difficulty settings. There is also the ability to play different skirmish levels while not playing in a campaign. There are also local multiplayer maps which allow for up to two players to play at once.
The game is great. It handles well for an RTS on the PlayStation, and the controls are intuitive. It also is very easy to pick up and put down. It gives the ability to save after each level, so one needn't worry about having to achieve too much in a sitting. The only down side is the amount of players that play this game on PSN is not that great, which does dampen the game's multiplayer ability. Lastly, one of the things that really impresses is the game's YouTube integration. Game videos are easily uploaded to YouTube's site which is a nice little addition.
Mushroom Wars is rated E (Everyone) by the ESRB for Mild Cartoon Violence.