As implied in adffa1c, a single segment-switching translation unit for
both rendering functions and game logic is the most straightforward
solution for those two games. Especially once you look at TH04, and
realize that the wildly chaotic order of the *_fg_render() functions in
the first code segment exactly matches the order of the *_update()
functions in the third.
Part of P0225, funded by Enderwolf, Blue Bolt, 32th System, and Yanga.
The .PTN functions, vector functions, and egc_copy_rect_1_to_0_1()
(finally!) from TH01, as well as playfld.hpp from all games(finally!),
together with a bunch of other functions in their vicinity.
Part of P0201, funded by Ember2528 and Yanga.