The Adventures of Square [Official Site] is a free retro FPS built with the GZDoom engine and it turns out it's pretty amusing.
You are Square, a wise-cracking hero who has to rescue Doctor Octagon from the Circle of Evil, a mysterious cult hellbent on the domination of Shape Land.
I wasn't familiar with it, until we had a handy email tip (thanks Luiz!) to notify us that the developers put out a second episode this month, which had been delayed for quite a while. Check out the wacky trailer:
Direct Link
For those who have played the first episode, this latest release changes the jump mechanics to add in "ledge forgiveness" and pseudo-bunnyhopping to make some of the platforming easier. It also comes with a revamped main menu, a Dual Oozi weapon, Defibs will electrocute you underwater and more. See the official news about it here.
The download for Linux is simply the main game file, which requires a copy of GZDoom. Once GZDoom is installed, it can simply be run with this in terminal:
gzdoom -iwad /path/to/downloaded/file/square1.pk3
The Adventures of Square is pretty odd, but I've actually come to appreciate the incredibly silly voice over along with the bizarre setting. The way enemies explode into a sticky mess, complete with eye-balls that bounce leaving only their boots when you kill them is the right amount of silly. Once you look past the initial goofiness, you will find a rather good FPS game with some fun level design.
Naturally, there's secrets to discover, keys to find to unlock more areas and other things you would expect in a Doom-like. It also worked perfectly in my testing. In addition to the two episodes, there's also a time attack mode for some extra fun.
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