STA $1FE11
STY $1FE12
INT #$13
LDA #$25
STA $1FE25
LDA #255
STA $FFE13
LDA #0
STA $FFE14
LDA #$FF
STA $1299
GAME
LDA $1FE11
LDY $1FE12
INT #$56
LDA $FFE19
STA $FFE17
LDX #$FF
STX $FFE15
JSR DRAWSCREEN
INT #$15
; test if escape key was pressed
LDY #$1B
INT #$19
CPY #0
BNE END



; fill the screen with black
LDX #0
INT #$57

JMP GAME ; loop back up to the start of the game loop
END BRK

; draw rectangle subroutine

DRAWRECT ; takes X,Y, and accumulator 
; ------------------------------------------------------------------
STA $1FE15
STX $1FE11
STY $1FE1
LDA $1FE25
ADC #5
STA $1FE25
MAJOR
LDY $1FE1
MINI 
LDA $1FE25
INT #$16
INY
LDA $1FE1
ADC #16
STA $1FE15
CPY $1FE15
BNE MINI
INX
LDA $1FE11
ADC #32
STA $1FE2
CPX $1FE2
BNE MAJOR
RTS

; draw of the screen subroutine

DRAWSCREEN
INT #$14
LDX #5
LDY #5
STX $1FE18
STY $1FE19

BIGLOOP
LOOP
LDA #$FF
LDX $1FE18
LDY $1FE19
JSR DRAWRECT
LDA $1FE18
ADC #36
STA $1FE18
CMP #0
BNE LOOP
LDX #5
STX $1FE18
LDA $1FE19
ADC #20
STA $1FE19
CMP #0
BNE BIGLOOP
RTS

; Add to Score subroutine
ADDSCORE
LDA $FFE19
ADC #1
STA $FFE19
RTS