If you are trying to play the game with more than 2 local players,
default screen size might be a little too small.
Fortunately, starting with v9900, this can be changed via a modding function called game_set_size(width, height)
So if you have 4 players and a standard FullHD screen, you could, for instance, do
/gml game_set_size(426, 240)
which would give just enough space for the additional HUDs to reside in.
If you are making total conversion mods, you may also find this to be useful.
While the game will do it's best to function at different sizes, keep in mind that this affects the balance (and "on-screen" checks), and is not how the game intended to be played.
You can always "add back" some difficulty with mods though.