Here are our frequently asked questions.
Gateway is compatible with Windows, Mac, and Linux/GNU machines.
In the main menu, press Ctrl+R, and the control scheme will reset to default (WASD + Space + Left Shift).
In the main menu, press Ctrl+M, and the music and SFX volumes will be set to 0. Press it again and you can quickly restore the volumes. The muted volume isn't saved between launches, though.
First, properly download and install the map pack; copy all the folders from the downloaded map-pack into the Gateway's directory. Then, launch it and select the Play option, then navigate to the map pack. Map-pack titles will be displayed on screen, but you might have to press left & right to find the right page your map pack is on. Select the map pack and have fun!
I made a whole page about this! See this page for a comprehensive guide. For more information about map-packs, see the wiki page.