This site is all about Gruntz. Here you will find all locations of red warps and locations of the secret ? switches. For every level there's a complete walkthrough, with lotz of links to screenshotz and hintz.

This walkthrough assumes you have installed the patch (version 1.01/1.10)
Although you can use this walkthrough for version 1.0 without problems I've included the old walkthrough for space level 3, because the way to solve the secret is different in version 1.0. For the differences between version 1.0 and 1.01/1.10 click the Version difference button.

When you need further help you can visit Gooroo's Gruntz site.

Gooroo's Gruntz site