Some technical details: I'm on Windows 10. My second monitor is 1920x1080, and my main monitor is 2560x1440. I'm launching the game from a folder inside my Documents folder (not Program Files).
Every time I launch Catlateral Damage, it will open on my second monitor. I can move it to my main monitor using [Win]+[Shift]+[Arrow Key], but if I try to up the resolution to 2560x1440, it will pop back over to my secondary monitor (this also happens on a resolution change downwards).
For now I've just been playing in 1920x1080 with the game attached to the top-left corner of my screen, but I'd really like to play in fullscreen on my big screen. Does anyone have any tips/workarounds? Is there maybe a setting I have to toggle that I missed?
Edit: The solution is to switch to windowed mode, move the game while it's in a window, then switch back to fullscreen. After that the game will stick with the monitor it's on.