You need to download both the exe and the pck and have them in the same folder.
Viewing post in One Shot, Many Kills jam comments
Ah, that was not clear for me. Perhaps you should make a .zip-file with everything in it, so only one downlaod has to be made. Would probably result in some more ratings :-)
I found your game pretty fun, but would love some more detailed graphics and a less steep difficulty curve. But the idea is promising!