I struggled a bit to figure this one out (in particular, I couldn't figure out why my gun would occasionally jam - I think using the item on the right fixed it?), but learning by trial-and-error was quite fun. The graphics were definitely the highlight, especially the opening/closing animation on the dome when transitioning between night and day.
I was very confused at first when I tried playing the web version, and nothing but a black screen, some rays of light, and the UI. The Linux build worked just fine, though.