I've tested it on both Ubuntu 17.10 and SteamOS and it works really well. I did have a weird issue initially on SteamOS where it gave me a black screen, resulting in me editing the unity prefs file directly to set the resolution, but that might be my 4K monitor causing issues. A quick edit solved it anyway, but the developer will look into it.
There's a few different game modes, all of them incredibly fun. I've been genuinly amused by Jump Gunners for taking a silly idea, but implementing it so incredibly well.
The Challenge mode is pretty simple, with you jumping around hitting various targets through each level trying to do it as quickly as you can. It is quite difficult, as the recoil from the weapons that you use to move can be mental to control. I've had many deaths, many close-calls and more deaths.
As for the other modes, sadly there are no bots, with the real meat of the game being the local multiplayer so you do need some friends available to properly enjoy it. I managed to rope in iAlwaysSin for a bit of local multiplayer fun, so here's what to expect from that:
Honestly, it's like playing a PVP version of Broforce and that's awesome.
Amusingly, it even has a Turkey Hunt mode, which is a bit of a parody of the retro classic Duck Hunt. I'll be honest, I spent far too long playing that mode because it brings back some very early gaming memories.
As far as gamepad support goes, it worked perfectly with the Steam Controller and the Logitech F310. Literally plug and play with everything working as expected.
The developer said that all updates and DLC will remain free, which sounds pretty awesome. If you need another game for local co-op that won't break the bank and doesn't require top-end hardware, this is well worth picking up.