((code
  (label main
    ; open terminal for debug
    (load-immediate $32 &terminal-namespace)
    (load-immediate $11 0)
    (syscall OPEN $32 $32 $11)

    ; Open screen
    ; use load immediate because it is a pointer to a string, not a value
    (load-immediate $0 &screen-namespace)
    (syscall OPEN $18 $0 $11) ; open(out Plex screen, in namespace, in flags)

    (load-immediate $1 4) ; offset for handle
    (add-nat $19 $18 $1)
    (get $0 $19) ; load handle

    (nat-to-string $5 $0)
    (push $32)
    (push $5)
    (call &pln)

    (load-immediate $1 8) ; offset for width
    (add-nat $19 $18 $1)
    (get $20 $19) ; load width

    (nat-to-string $5 $20)
    (push $32)
    (push $5)
    (call &pln)

    (load-immediate $1 12) ; offset for size
    (add-nat $19 $18 $1)
    (get $22 $19) ; load size   

    (nat-to-string $5 $22)
    (push $32)
    (push $5)
    (call &pln)

    (load-immediate $1 16) ; offset for screen buffer
    (add-nat $21 $18 $1)

    (nat-to-string $5 $21)
    (push $32)
    (push $5)
    (call &pln)

    ; open mouse
    (load-immediate $16 &mouse-namespace)
    (syscall OPEN $15 $16 $11) ; open(out Plex mouse, in namespace, in flags)

    (load-immediate $1 4) ; offset for handle
    (add-nat $19 $15 $1)

    (nat-to-string $5 $19)
    (push $32)
    (push $5)
    (call &pln)
    (get $16 $19) ; load handle

    (syscall WRITE $0 $21 $22) ; redraw

    (load-immediate $3 16)
    (label draw-loop
      ; load mouse click data
	  	(syscall READ $16 $2 $3 $15)
      (load-immediate $5 16) ; offset for btn1
      (add-nat $6 $15 $5)
      (get-8 $9 $6) ; load btn1 pressed

      (jump-eq-nat &draw-loop $9 $11)

      (load-immediate $5 8) ; offset for x
      (add-nat $6 $5 $2)
      (get $7 $6) ; load x
      (load-immediate $5 12) ; offset for y
      (add-nat $6 $5 $2)
      (get $8 $6) ; load y

      ; Compute start address: y*width + x
      (mul-nat $30 $8 $20)        ; $15 = y * width
      (add-nat $30 $30 $7)        ; $15 += x
      (add-nat $30 $30 $21)       ; $15 += pixel_offset
      (load-immediate $1 4) ; need to add offset for fat pointer size
      (add-nat $30 $30 $1)

      (load $3 &WHITE) ; color
      (store-8 $30 $3) ; draw color at screen [x,y]
      (syscall WRITE $0 $21 $22) ; redraw

      (jump &draw-loop))
    (halt))
  (label pln 
		(load-immediate $3 &new-line)
		(pop $1)
    (pop $0)

    (load-immediate $5 4) ; offset for handle
    (add-nat $6 $0 $5)
    (get $7 $6) ; load handle

		(string-length $2 $1)
		(syscall WRITE $7 $1 $2)
		(string-length $4 $3)
		(syscall WRITE $7 $3 $4)
		(return)))
(data
  (label screen-namespace "/dev/screen/0")
  (label mouse-namespace "/dev/mouse/0")
  (label terminal-namespace "/dev/term/0")
	(label new-line "\n")
	(label WHITE 255)))