Reset Resolution of X Server after Program Crash

Today I played Warzone 2100. In the second mission in the beta camp I gave orders to build defenses, factories and other things. Then I loaded the transporter and started it to get to the missions map. But then the program crashed and left the X server in a pretty low resolution.

Now how do I reset the resolution?

Easy, the following line does the trick:

xrandr -s 1920x1080

You may have to choose the proper resolution for your monitor. Just entering xrandr without any options shows the available resolutions.