I always use reusable code where possible , and even a TMS1100 is no exception. I've written a slightly demented bit of code this evening which takes a digit (0-9) and stores a pixel version of it in memory.
Not difficult in most processors, but in an TMS1100 it has to fit in 64 bytes otherwise its pretty useless as a subroutine (branching to another page is possible - you can go the the opposite chapter, I think, but not a different page in the same chapter, because PB is used for the subroutine return address and the page register.
Just need to write some code to physically render it to the LCD.
Not sure what sort of game to write yet. A version of the old Bombing game where you go left to right across the screen trying to flatten buildings, maybe, as a first run. Or maybe something else.
Coding in these things often uses a FSM type approach, rather than a modular approach. It's difficult to be modular when you only have one level of subroutine, and fairly small subroutines.