I revived a prototype platformer I started in college called Terminus. For me, it was mostly an excuse to fiddle with chatbots as a method of driving the plot forward, but I found an extra interesting twist: an in-game assembly language that allows the user to solve programming problems.
Here’s a general overview of the CPU:
- 256 bytes of memory.
- 1 byte instructions with up to three operators.
- No registers, but every instruction allows dereferencing and writing to an arbitrary memory output.
Here’s some sample code which puts calculates if a value on _BUS0 is prime or not, writing 1 for primes, 2 for composites, and 0 for not yet finished.
;; Prime directive. ;; Assorted one-byte primes are coming in on BUS0. ;; Write 1 to BUS1 if they're prime numbers or 2 if they're composite. ;; Keep at 0 while processing. ;; 0 and 1 are not prime. JMP _START ; Set aside some protected memory at the start of the program. BUS0: 0x00 BUS1: 0x00 TARGET: 0x00 DIVISOR: 0x00 TEMP: 0x00 ;; Begin. START: ; Save the values from _BUS0 just in case it changes. ; Init. MOV *BUS0 TARGET MOV 2 DIVISOR MOV 0 BUS1 ; Main loop. LOOP: MOD *TARGET *DIVISOR TEMP JE *TEMP 0 DIVISOR_FOUND ; Otherwise this doesn't divide evenly ADD 1 *DIVISOR DIVISOR ; Increase our number by 1. JE *DIVISOR *TARGET NO_DIVISOR_FOUND ; If we're at the target, no divisor. JE 0 0 LOOP DIVISOR_FOUND: MOV 1 BUS1 JE 0 0 START NO_DIVISOR_FOUND: MOV 2 BUS1 JE 0 0 START
It’s a nice change of pace from ML work to do some CPU design. The choice to leave off a register actually turned out to simplify the code, too. Here are some screenshots: