Replay a chapter in Magicka?

Solution 1:

Since the update 1.4.3.1, an option allows the player to revisit old chapters in a campaign. You just have to click on the name of the chapter on the select screen.

Changelog for Magicka Patch 1.4.3.1 2011-11-15

• Added saveable checkpoints. Checkpoints will now save your progress up to that point.

• Added a automatic-revive fairy for single player games.

• Added an option to revisit old chapters in a campaign.

• Improved server browser usability.

• Improved body collision detection and overall physics.

Solution 2:

You can restart any chapter you have to point on map and load chapter you want.