without asm

 set romsize 4k

 dim mapx = a
 dim mapy = b
 dim pfy = c
 const mem = $A4

 COLUPF=$FF
 COLUBK=$00

 playfield:
 ....XX...XX...XXX...XX...XX....
 ....X.X..X.X..X....X....X......
 ....XX...XX...XX....X....X.....
 ....X....X.X..X......X....X....
 ....X....X.X..XXX..XX...XX.....
 ...............................
 .....XX..XX....X....XX..XXX....
 ....X....X.X..X.X..X....X......
 .....X...XX...XXX..X....XX.....
 ......X..X....X.X..X....X......
 ....XX...X....X.X...XX..XXX....
end

PROGRAMLOOP
 if joy0fire then let z = z | 1
 if !joy0fire && z then gosub DRAW_MAP

 drawscreen

 goto PROGRAMLOOP

DRAW_MAP
 if mapy > 39 then mapy = 0 else mapy = mapy + 4
 for pfy = 0 to 40 step 4

    for mapx = 0 to 3
    temp1 = mapy | mapx
    temp2 = pfy | mapx
    mem[temp2] = map[temp1]
    next
 if mapy > 39 then mapy = 0 else mapy = mapy + 4
 next
 z = 0
 return

 data map
 %00001010, %00010111, %10001110, %00000000,
 %00001010, %00010001, %10001010, %00000000,
 %00001110, %00010011, %10001010, %00000000,
 %00001010, %00010001, %10001010, %00000000,
 %00001010, %01110111, %11101110, %00000000,
 %00000000, %00000000, %00000000, %00000000,
 %00001000, %01100100, %01110010, %00111000,
 %00001000, %10010100, %01001010, %01001000,
 %00000101, %10010010, %01110010, %01001000,
 %00000010, %01100001, %01001011, %00111011,
 %00000000, %00000000, %00000000, %00000000,
 %00000000, %00000000, %00000000, %00000000
end