Perspective projection only works for FOV < 180deg. At FOV = 180 the projected coordinate has to be +inf and it won’t work, so games that support FOV beyond 180

Perspective projection only works for FOV < 180deg. At FOV = 180 the projected coordinate has to be +inf and it won’t work, so games that support FOV beyond 180 stitches multiple viewports, either on display or by having multiple displays.