; C64 Assembly for Simulated Ray Casting
; This simulates a 2D “ray tracing” effect
; Reality: It’s just rendering basic ray-cast walls in 2D space

.org $0801 ; Program start for BASIC SYS
.word $080A, 0 ; Link for BASIC
.byte $9E ; SYS opcode
.asc “2061” ; SYS 2061 (to start at $080D)
.byte 0

start:
lda #$00 ; Clear screen
jsr $E544

ldx #$00 ; Set X position of rays
loop_cast:
jsr raycast ; Call raycasting subroutine
inx
cpx #40 ; Loop for 40 columns (screen width)
bne loop_cast

rts ; End program

raycast:
lda #$00 ; Initialize distance
sta distance
lda #$FF ; Set max wall brightness
sta brightness

ldy #0 ; Loop for rays
loop_ray:
lda (ray_pos), y ; Simulate a ray calculation
cmp wall_distance
bcc render_pixel ; If hit, render pixel
iny
cpy #100 ; Max ray length
bne loop_ray

rts ; Ray missed

render_pixel:
lda brightness ; Brightness decay
sta screen_buffer,x ; Draw pixel
rts

distance:
.byte $00 ; Placeholder for distance
brightness:
.byte $FF ; Placeholder for brightness

screen_buffer:
.res 1000, $00 ; Space for screen buffer
wall_distance:
.byte $10 ; Fake wall distance