; Kill the Bit
; Original by Dean McDaniel for the Altair 8800, May 15, 1975
; https://altairclone.com/downloads/killbits.pdf
; https://archive.is/dQp9r
;
; Port to Balaurul Unu by Chris Musei-Sequeira, April 4, 2025
;
; ** Game instructions by Dean McDaniel **
: "Kill the rotating bit. If you miss the lit bit, another
; bit turns on leaving two bits to destroy. Quickly
; toggle the switch, don't leave the switch in the up
; position. Before starting, make sure all the switches
; are in the down position."
;
; ** How to modify source code to change game speed **
; To speed up the game, remove NOP instructions from the NOP
; list below. To slow the game down, add NOP instructions.

ORIGIN 0000

0000    LDI 4000            ; Load accumulator with leftmost bit on

.main_loop:
0002    OUT                 ; Display accumulator at OUT register
0003    STA temp            ; Store accumulator to temporary storage
0005    LDI 7777            ; Load accumulator for time delay
    
.delay_loop:
0007    DEC                 ; Decrement accumulator

0010    NOP                 ; Add or remove NOPs to slow or speed up game
0011    NOP
0012    NOP
0013    NOP
0014    NOP
0015    NOP
0016    NOP
0017    NOP

0020    NOP
0021    NOP
0022    NOP
0023    NOP
0024    NOP
0025    NOP
0026    NOP
0027    NOP

0030    JNZ .delay_loop    ; If accumulator non-zero, loop for time delay    

0032    IN                 ; Scan input switches into accumulator
0033    XOA temp           ; XOR accumulator with value in temp storage
0035    ROR                ; Rotate accumulator right
0036    JMP .main_loop     ; Go back to start

temp:
0077    ORIGIN 0077


****** ASSEMBLED ******

0020 4000 0002 0051 0077 0020 7777 0011 
0000 0000 0000 0000 0000 0000 0000 0000 
0000 0000 0000 0000 0000 0000 0000 0000 
0064 0007 0003 0047 0077 0014 0060 0002