So we can make it an arbitrary size, maybe, if necessary. framebuffers are expensive, so we defer creation of them until postprocessing is switched on for the first time.
So far, we have: titles, game setup, countdown, playing. Still to add: win, lose, paused. And probably some others. Also fixed an annoying bug with text rendering where overlapped text wasn't getting shown. It was because they were all getting drawn at the same depth, but the depth func was set to LESS rather than LEQUAL.