Some game engines (PICO-8, Octo) have a set resolution that can't be changed.
Is it allowed to make a game with a resolution that's higher than the 3310's resolution, as long as you only actually use 84x48 pixels within that viewport?
Alternatively, is it allowed to make a game with a lower resolution than 84x48?
I forgot about those engines! The game resolution must be 84x48 in landscape or portrait so if the engine cannot scale/work in that requirement it would not be allowed.
I can only speak in Game Maker terms but your camera should be 84x48/48x84. You can leave the viewport at the required resolution or scale it for players so they are not looking at a tiny game window.
If you want to work in a lower resolution as an artistic choice it would have to be scaled up to the required resolution.
I hope that makes sense and answers your questions!
I think really the question is whether we're allowed to do something along the lines of letterboxing a game down to 84x48. For example, here's a very simple "SuperChip" CHIP-8 program which logically runs at 128x64 pixels, but which fills the border with a solid matte. The light-colored region of the screen, where one would draw game graphics, is 84x48: http://johnearnest.github.io/Octo/index.html?key=aQPWzRRq
Octo can use any colors for its palette (there are 2-color and 4-color palette modes available, the former of which is suitable for this Jam), but I think PICO-8 is off the table because its palette cannot be altered to meet the jam requrements.
