# move pacman, starting with initialization
.org 0x00000000
.align 8
.set noreorder
main:		addi $3,$0,8		# 8 rows/grid 
		addi $6,$0,1315		# bonus position
		addi $7,$0,3845		# gost1 pos
		addi $8,$0,5150		# gost2 pos
		addi $9,$0,5764		# gost3 pos
		addi $4,$0,0		# rom addr, starts 
brow:		lw   $5,40($4)		# addr of bonus
		lw   $5,40($4)		# addr of 
		sw   $5,0($6)		# draw bonus
		sw   $5,1($6)
		sw   $5,2($6)
		sw   $5,3($6)
		lw   $5,48($4)
		lw   $5,48($4)
		sw   $5,0($7)
		lw   $5,56($4)
		lw   $5,56($4)
		sw   $5,0($8)
		lw   $5,64($4)
		lw   $5,64($4)
		sw   $5,0($9)
		addi $3,$3,-1		# decr row
		addi $4,$4,1		# incr $4
		beq  $3,$0,pac		# loop out if 0
		addi $6,$6,40		# mem offset = 40 words
		addi $7,$7,40
		addi $8,$8,40
		addi $9,$9,40
		j    brow
pac:		addi $3,$0,8		# 8 rows/grid 
		addi $6,$0,4820		# init position
		addi $4,$0,0		# rom addr, starts 
ub1g:		lw   $5,0($4)		# addr of 'X'
		lw   $5,0($4)		# addr of 'X'
		sw   $5,0($6)		# draw top wall
		addi $3,$3,-1		# decr row
		addi $4,$4,1		# incr $4
		beq  $3,$0,init		# loop out if 0
		addi $6,$6,40		# mem offset = 40 words
		j    ub1g		
init:		addi $18,$0,6		# col limit
		addi $17,$0,38		# col limit
		addi $16,$0,23		# row limit
		addi $9,$0,20		# init col
		addi $8,$0,15		# init row
		addi $15,$0,1		# up
		addi $14,$0,2		# right
		addi $13,$0,4		# down
		addi $12,$0,8		# left
		addi $11,$0,32767	# prep joystick ram
		addi $11,$11,1
		addi $24,$0,0		# offset of bmp_mem
game_loop:	addi $10,$0,0		# clear reg
		lw $10,0($11)		# read direction
		lw $10,0($11)
		beq $10,$15,up
		beq $10,$14,right
		beq $10,$13,down
		beq $10,$12,left
		j game_loop
up:		slt $5,$18,$8		# row>6?
		beq $5,$15,up_init	# true: go up 1 grid
		j game_loop		
up_init:	addi $8,$8,-1		# row--
		add $5,$0,$9		# record previous col
		addi $2,$8,1		# record previous row
		addi $24,$0,8		# offset of bmp_mem
		j update
right:		slt $5,$9,$17		# col<38?
		beq $5,$15,rt_init	# true: go right 1 grid
		j game_loop		
rt_init:	addi $9,$9,1		# col++
		addi $5,$9,-1		# record previous col
		add  $2,$0,$8		# record previous row
		addi $24,$0,16		# offset of bmp_mem
		j update
down:		slt $5,$8,$16		# row<23?
		beq $5,$15,dn_init	# true: go down 1 grid
		j game_loop		
dn_init:	addi $8,$8,1		# row++
		add $5,$0,$9		# record previous col
		addi $2,$8,-1		# record previous row
		addi $24,$0,24		# offset of bmp_mem
		j update
left:		slt $5,$15,$9		# col>1?
		beq $5,$15,lt_init	# true: go left 1 grid
		j game_loop		
lt_init:	addi $9,$9,-1		# col--
		addi $5,$9,1		# record previous col
		add  $2,$0,$8		# record previous row
		addi $24,$0,32		# offset of bmp_mem
		j update
update:		addi $3,$0,320		# start addr = screen row*320+col
		addi $20,$0,0		# current screen row
		addi $19,$0,0		# previous screen row
sum:		add $20,$20,$8		# $20+=current row
		add $19,$19,$2		# $19+=previous row
		addi $3,$3,-1
		beq $3,$0,start_addr
		j sum			# for product of row*40
start_addr:	add $6,$20,$9		# current start addr
		add $7,$19,$5		# previous start addr		
		addi $3,$0,8		# 8 rows
		add $4,$24,$0		# $4=bmp offset
		addi $21,$0,16000
		addi $22,$0,0
delay0:		addi $22,$22,1
		addi $23,$0,100
delay1:		addi $23,$23,-1
		nop
		beq $23,$0,cont
		j delay1
cont:		beq $22,$21,next_row
		j delay0
next_row:	lw $5,0($4)		
		lw $5,0($4)		
		sw $5,0($6)		# draw ball
		sw $0,0($7)
		addi $4,$4,1
		addi $6,$6,40		# row offset = 40
		addi $7,$7,40
		addi $3,$3,-1
		beq $3,$0,game_loop
		j next_row