diff --git a/test/paint-bw.asm.lisp b/test/paint-bw.asm.lisp
index b00b1eb..4c45753 100644
--- a/test/paint-bw.asm.lisp
+++ b/test/paint-bw.asm.lisp
@@ -19,26 +19,16 @@
     (load-offset-32 $16 $15 4) ; load handle
 
     ; outline_swatch(screen, BLACK, 1, 1);
-    (push $21)
-    (push $20)
     (load-absolute-32 $1 &BLACK)
-    (push $1)
     (load-immediate $12 1)
-    (push $12)
     (load-immediate $13 1)
-    (push $13)
-    (call &draw-outlined-swatch)
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
 
     ; outline_swatch(screen, WHITE, 1, 1);
-    (push $21)
-    (push $20)
     (load-absolute-32 $1 &WHITE)
-    (push $1)
     (load-immediate $12 21)
-    (push $12)
     (load-immediate $13 1)
-    (push $13)
-    (call &draw-outlined-swatch)    
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
     
     ; screen.draw();
     (syscall WRITE $0 $21 $22)
@@ -57,45 +47,26 @@
       (load-immediate $14 20) ; box size
 
       ; first row
-      (push $21)
-      (push $20)
       (load-absolute-32 $1 &BLACK)
-      (push $1)
       (load-immediate $12 1)
-      (push $12)
       (load-immediate $13 1)
-      (push $13)
-      (call &draw-outlined-swatch)
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
       
-      ; set_color_if_clicked(box_size, box_y, box_x, click_y, click_x, color)
-      (call &set-color-if-clicked ($7 $8 $12 $13 $14 $5) nil)
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
-      (push $21)
-      (push $20)
       (load-absolute-32 $1 &WHITE)
-      (push $1)
       (load-immediate $12 21)
-      (push $12)
       (load-immediate $13 1)
-      (push $13)
-      (call &draw-outlined-swatch)
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
 
-      ; set_color_if_clicked(box_size, box_y, box_x, click_y, click_x, color)
-      (call &set-color-if-clicked ($7 $8 $12 $13 $14 $5) nil)
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
       (syscall WRITE $0 $21 $22)
 
       (load-absolute-32 $22 &SELECTED-COLOR) ; color
       (load-immediate $1 5) ; size of brush
 
-      (push $21) ;base
-      (push $20) ;width
-      (push $22) ; color
-      (push $7) ;x
-      (push $8) ;y
-      (push $1)
-      (push $1)
-      (call &draw-box)
+      (call &draw-box ($21 $20 $22 $7 $8 $1 $1) nil)
 
       (jump &draw-loop))
 
@@ -103,13 +74,13 @@
     (halt))
 
   (label set-color-if-clicked 
-    ; (click_x, click_y, box_x, box_y, box_size, color)
+    ; (click_x, click_y, box_x, box_y, color, box_size)
 
     ; Compute right = box_x + box_size
-    (add-int $6 $2 $4)    ; $6 = right edge
+    (add-int $6 $2 $5)    ; $6 = right edge
     
     ; Compute bottom = box_y + box_size  
-    (add-int $7 $3 $4)    ; $7 = bottom edge
+    (add-int $7 $3 $5)    ; $7 = bottom edge
 
     ; Bounds check: x in [box_x, right] and y in [box_y, bottom]
     (jump-lt-int &fail $0 $2)
@@ -118,87 +89,56 @@
     (jump-gt-int &fail $1 $7)
 
     (load-immediate $10 &SELECTED-COLOR)
-    (store-absolute-8 $10 $5)
+    (store-absolute-8 $10 $4)
 
     (label fail)
     (return nil))
 
   (label draw-outlined-swatch
-    (pop $0)
-    (pop $1)   ; color
-    (pop $2)   ; x
-    (pop $3)   ; y
-    (pop $20)
+    ; (base, color, x, y, width)
 
     ; Constants
-    (load-absolute-32 $4 &GRAY)
+    (load-absolute-32 $5 &GRAY)
     (load-absolute-32 $10 &SELECTED-COLOR)
     (jump-eq-int &set-selected $10 $1)
-    (jump-eq-int &end-set-selected $4 $4)
+    (jump-eq-int &end-set-selected $5 $5)
     (label set-selected)
-    (load-absolute-32 $4 &DARK-GRAY)
+    (load-absolute-32 $5 &DARK-GRAY)
     (label end-set-selected)
 
-    (load-immediate $5 20)       ; outline size
-    (load-immediate $6 17)       ; fill size
-    (load-immediate $7 2)        ; offset
+    (load-immediate $6 20)       ; outline size
+    (load-immediate $7 17)       ; fill size
+    (load-immediate $8 2)        ; offset
 
-    (push $0)     ; base
-    (push $20)     ; width
-    (push $4)      ; color (gray)
-    (push $2)      ; x
-    (push $3)      ; y
-    (push $5)      ; width (20)
-    (push $5)      ; height (20)
-    (call &draw-box)
+    (call &draw-box ($0 $4 $5 $2 $3 $6 $6) nil)
 
-    (add-int $8 $2 $7)   ; x + 2
-    (add-int $9 $3 $7)   ; y + 2
+    (add-int $9 $2 $8)    ; x + 2
+    (add-int $10 $3 $8)   ; y + 2
 
-    (push $0)     ; base
-    (push $20)     ; width
-    (push $1)      ; color (original)
-    (push $8)      ; x + 2
-    (push $9)      ; y + 2
-    (push $6)      ; width (17)
-    (push $6)      ; height (17)
-    (call &draw-box)
+    (call &draw-box ($0 $4 $1 $9 $10 $7 $7) nil)
 
     (return nil))
 
-  ; draw-box(color, x, y)
-  ; Pops: y, x, color
   (label draw-box
-    ; Pop arguments (reverse order)
-    (pop $14)        ; height
-    (pop $12)        ; width
-    (pop $13)        ; y_start
-    (pop $11)        ; x_start
-    (pop $3)         ; color
-    (pop $2)         ; width
-    (pop $21)        ; base
-
-    ; Constants
-    (load-immediate $1 1)        ; increment
+    ; (base, screen_width, color, x_start, y_start, width, height)
 
     ; Compute start address: base + y*640 + x
-    (mul-int $15 $13 $2)         ; $15 = y * 640
-    (add-int $15 $15 $11)        ; $15 += x
-    (add-nat $15 $21 $15)       ; $15 = base + pixel_offset
+    (mul-int $15 $4 $1)        ; $15 = y * 640
+    (add-int $15 $15 $3)       ; $15 += x
+    (add-nat $15 $0 $15)       ; $15 = base + pixel_offset
     (load-immediate $25 4)
-    (add-nat $15 $15 $25) ; need to add offset for fat pointer size
-    (register-move $4 $15)
+    (add-nat $15 $15 $25)      ; need to add offset for fat pointer size
 
     ; Outer loop: height times
-    (register-move $5 $14)       ; $5 = row counter
+    (load-immediate $30 1)     ; increment
 
     (label draw-box-outer
-      (add-int $6 $4 $12)        ; $6 = row end = current + width
-      (register-move $7 $4)      ; $7 = pixel pointer
-      (memset-8 $7 $3 $12)       ; draw row
-      (add-int $4 $4 $2)         ; next row (+= 640)
-      (sub-int $5 $5 $1)         ; decrement row count
-      (jump-gt-int &draw-box-outer $5 0))
+      (add-int $27 $15 $5)     ; $27 = row end = current + width
+      (register-move $29 $15)   ; $7 = pixel pointer
+      (memset-8 $29 $2 $5)      ; draw row
+      (add-int $15 $15 $1)     ; next row (+= 640)
+      (sub-int $6 $6 $30)    ; decrement row count
+      (jump-gt-int &draw-box-outer $6 0))
     (return nil)))
 (data
 	(label screen-namespace "/dev/screen/0")
diff --git a/test/paint-bw.rom b/test/paint-bw.rom
new file mode 100644
index 0000000..5b276e1
Binary files /dev/null and b/test/paint-bw.rom differ
diff --git a/test/paint.asm.lisp b/test/paint.asm.lisp
index 0b32ee2..faf2863 100644
--- a/test/paint.asm.lisp
+++ b/test/paint.asm.lisp
@@ -4,7 +4,7 @@
     ; use load immediate because it is a pointer to a string, not a value
     (load-immediate $0 &screen-namespace)
     (load-immediate $11 0)
-    (syscall OPEN $18 $0 $11) ; Screen screen = open(namespace, flags)
+    (syscall OPEN $18 $0 $11) ; open(out Plex screen, in namespace, in flags)
 
     (load-offset-32 $0 $18 4) ; load handle
     (load-offset-32 $20 $18 8) ; load width
@@ -14,21 +14,61 @@
 
     ; open mouse
     (load-immediate $16 &mouse-namespace)
-    (syscall OPEN $15 $16 $11) ; Mouse mouse = open(namespace, flags)
+    (syscall OPEN $15 $16 $11) ; open(out Plex mouse, in namespace, in flags)
 
     (load-offset-32 $16 $15 4) ; load handle
 
-    ; outline_swatch(screen, BLACK, 1, 1, width);
+    ; outline_swatch(screen, BLACK, 1, 1);
     (load-absolute-32 $1 &BLACK)
     (load-immediate $12 1)
     (load-immediate $13 1)
     (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
 
-    ; outline_swatch(screen, WHITE, 1, 1, width);
+    ; outline_swatch(screen, WHITE, 1, 1);
     (load-absolute-32 $1 &WHITE)
     (load-immediate $12 21)
     (load-immediate $13 1)
-    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+
+    (load-absolute-32 $1 &CHARCOAL)
+    (load-immediate $12 1)
+    (load-immediate $13 21)
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+
+    (load-absolute-32 $1 &DARK-GRAY)
+    (load-immediate $12 21)
+    (load-immediate $13 21)
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+
+    (load-absolute-32 $1 &RED)
+    (load-immediate $12 1)
+    (load-immediate $13 41)
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+
+    (load-absolute-32 $1 &ORANGE)
+    (load-immediate $12 21)
+    (load-immediate $13 41)
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+
+    (load-absolute-32 $1 &YELLOW)
+    (load-immediate $12 1)
+    (load-immediate $13 61)
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+
+    (load-absolute-32 $1 &GREEN)
+    (load-immediate $12 21)
+    (load-immediate $13 61)
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+
+    (load-absolute-32 $1 &BLUE)
+    (load-immediate $12 1)
+    (load-immediate $13 81)
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+
+    (load-absolute-32 $1 &PURPLE)
+    (load-immediate $12 21)
+    (load-immediate $13 81)
+    (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
     
     ; screen.draw();
     (syscall WRITE $0 $21 $22)
@@ -46,132 +86,82 @@
 
       (load-immediate $14 20) ; box size
 
-      ; first row
+      ; outline_swatch(screen, BLACK, 1, 1);
       (load-absolute-32 $1 &BLACK)
       (load-immediate $12 1)
       (load-immediate $13 1)
       (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
-      
-      ; set_color_if_clicked(color, click_x, click_y, box_x, box_y, 20);
-      (call &set-color-if-clicked ($1 $7 $8 $12 $13 $14) nil)
-
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
+      ; outline_swatch(screen, WHITE, 1, 1);
       (load-absolute-32 $1 &WHITE)
       (load-immediate $12 21)
       (load-immediate $13 1)
-      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
-      
-      ; set_color_if_clicked(color, click_x, click_y, box_x, box_y, 20);
-      (call &set-color-if-clicked ($1 $7 $8 $12 $13 $14) nil)
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
-      ; row 2
       (load-absolute-32 $1 &CHARCOAL)
       (load-immediate $12 1)
       (load-immediate $13 21)
-      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
-      
-      ; set_color_if_clicked(color, click_x, click_y, box_x, box_y, 20);
-      (call &set-color-if-clicked ($1 $7 $8 $12 $13 $14) nil)
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
-      (push $21)
-      (push $20)
       (load-absolute-32 $1 &DARK-GRAY)
-      (push $1)
       (load-immediate $12 21)
-      (push $12)
       (load-immediate $13 21)
-      (push $13)
-      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
-      
-      ; set_color_if_clicked(color, click_x, click_y, box_x, box_y, 20);
-      (call &set-color-if-clicked ($1 $7 $8 $12 $13 $14) nil)
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
-      ; row 3
-      (push $21)    
-      (push $20)  
       (load-absolute-32 $1 &RED)
-      (push $1)
       (load-immediate $12 1)
-      (push $12)
       (load-immediate $13 41)
-      (push $13)
-      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
-      
-      ; set_color_if_clicked(color, click_x, click_y, box_x, box_y, 20);
-      (call &set-color-if-clicked ($1 $7 $8 $12 $13 $14) nil)
-
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
       (load-absolute-32 $1 &ORANGE)
       (load-immediate $12 21)
       (load-immediate $13 41)
-      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
-      
-      ; set_color_if_clicked(color, click_x, click_y, box_x, box_y, 20);
-      (call &set-color-if-clicked ($1 $7 $8 $12 $13 $14) nil)
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
-      ; row 3
       (load-absolute-32 $1 &YELLOW)
       (load-immediate $12 1)
       (load-immediate $13 61)
-      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
-      
-      ; set_color_if_clicked(color, click_x, click_y, box_x, box_y, 20);
-      (call &set-color-if-clicked ($1 $7 $8 $12 $13 $14) nil)
-
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
       (load-absolute-32 $1 &GREEN)
       (load-immediate $12 21)
       (load-immediate $13 61)
-      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
-      
-      ; set_color_if_clicked(color, click_x, click_y, box_x, box_y, 20);
-      (call &set-color-if-clicked ($1 $7 $8 $12 $13 $14) nil)
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
-      ; row 4
       (load-absolute-32 $1 &BLUE)
       (load-immediate $12 1)
       (load-immediate $13 81)
-      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
-      
-      ; set_color_if_clicked(color, click_x, click_y, box_x, box_y, 20);
-      (call &set-color-if-clicked ($1 $7 $8 $12 $13 $14) nil)
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
       (load-absolute-32 $1 &PURPLE)
       (load-immediate $12 21)
       (load-immediate $13 81)
-      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil)
-      
-      ; set_color_if_clicked(color, click_x, click_y, box_x, box_y, 20);
-      (call &set-color-if-clicked ($1 $7 $8 $12 $13 $14) nil)
+      (call &draw-outlined-swatch ($21 $1 $12 $13 $20) nil) 
+      (call &set-color-if-clicked ($7 $8 $12 $13 $1 $14) nil)
 
       (syscall WRITE $0 $21 $22)
 
       (load-absolute-32 $22 &SELECTED-COLOR) ; color
       (load-immediate $1 5) ; size of brush
 
-      (push $21) ;base
-      (push $20) ;width
-      (push $22) ; color
-      (push $7) ;x
-      (push $8) ;y
-      (push $1)
-      (push $1)
-      ; draw_box(brush_size, )
-      (call &draw-box ($1 $1 $8 $7 $22 $20 $21) nil)
+      (call &draw-box ($21 $20 $22 $7 $8 $1 $1) nil)
 
       (jump &draw-loop))
 
     ; Flush and halt
     (halt))
 
-  (label set-color-if-clicked
-    ; Pop inputs from stack (in reverse order of pushing)
-    (pop $11)       ; $11 = color
-    (pop $0)        ; $0 = click_x
-    (pop $1)        ; $1 = click_y
-    (pop $2)        ; $2 = box_x
-    (pop $3)        ; $3 = box_y
-    (pop $5)        ; $5 = box_size
+  (label set-color-if-clicked 
+    ; (click_x, click_y, box_x, box_y, color, box_size)
 
     ; Compute right = box_x + box_size
     (add-int $6 $2 $5)    ; $6 = right edge
@@ -186,88 +176,57 @@
     (jump-gt-int &fail $1 $7)
 
     (load-immediate $10 &SELECTED-COLOR)
-    (store-absolute-8 $10 $11)
+    (store-absolute-8 $10 $4)
 
     (label fail)
-    (return))
+    (return nil))
 
   (label draw-outlined-swatch
-    (pop $3)   ; y
-    (pop $2)   ; x
-    (pop $1)   ; color
-    (pop $20)
-    (pop $21)
+    ; (base, color, x, y, width)
 
     ; Constants
-    (load-absolute-32 $4 &GRAY)
+    (load-absolute-32 $5 &GRAY)
     (load-absolute-32 $10 &SELECTED-COLOR)
     (jump-eq-int &set-selected $10 $1)
-    (jump-eq-int &end-set-selected $4 $4)
+    (jump-eq-int &end-set-selected $5 $5)
     (label set-selected)
-    (load-absolute-32 $4 &DARK-GRAY)
+    (load-absolute-32 $5 &DARK-GRAY)
     (label end-set-selected)
 
-    (load-immediate $5 20)       ; outline size
-    (load-immediate $6 17)       ; fill size
-    (load-immediate $7 2)        ; offset
+    (load-immediate $6 20)       ; outline size
+    (load-immediate $7 17)       ; fill size
+    (load-immediate $8 2)        ; offset
 
-    (push $21)     ; base
-    (push $20)     ; width
-    (push $4)      ; color (gray)
-    (push $2)      ; x
-    (push $3)      ; y
-    (push $5)      ; width (20)
-    (push $5)      ; height (20)
-    (call &draw-box)
+    (call &draw-box ($0 $4 $5 $2 $3 $6 $6) nil)
 
-    (add-int $8 $2 $7)   ; x + 2
-    (add-int $9 $3 $7)   ; y + 2
+    (add-int $9 $2 $8)    ; x + 2
+    (add-int $10 $3 $8)   ; y + 2
 
-    (push $21)     ; base
-    (push $20)     ; width
-    (push $1)      ; color (original)
-    (push $8)      ; x + 2
-    (push $9)      ; y + 2
-    (push $6)      ; width (17)
-    (push $6)      ; height (17)
-    (call &draw-box)
+    (call &draw-box ($0 $4 $1 $9 $10 $7 $7) nil)
 
-    (return))
+    (return nil))
 
-  ; draw-box(color, x, y)
-  ; Pops: y, x, color
   (label draw-box
-    ; Pop arguments (reverse order)
-    (pop $14)        ; height
-    (pop $12)        ; width
-    (pop $13)        ; y_start
-    (pop $11)        ; x_start
-    (pop $3)         ; color
-    (pop $2)         ; width
-    (pop $21)        ; base
-
-    ; Constants
-    (load-immediate $1 1)        ; increment
+    ; (base, screen_width, color, x_start, y_start, width, height)
 
     ; Compute start address: base + y*640 + x
-    (mul-int $15 $13 $2)         ; $15 = y * 640
-    (add-int $15 $15 $11)        ; $15 += x
-    (add-nat $15 $21 $15)       ; $15 = base + pixel_offset
+    (mul-int $15 $4 $1)        ; $15 = y * 640
+    (add-int $15 $15 $3)       ; $15 += x
+    (add-nat $15 $0 $15)       ; $15 = base + pixel_offset
     (load-immediate $25 4)
-    (add-nat $15 $15 $25) ; need to add offset for fat pointer size
-    (register-move $4 $15)
+    (add-nat $15 $15 $25)      ; need to add offset for fat pointer size
 
     ; Outer loop: height times
-    (register-move $5 $14)       ; $5 = row counter
+    (load-immediate $30 1)     ; increment
 
     (label draw-box-outer
-      (add-int $6 $4 $12)        ; $6 = row end = current + width
-      (register-move $7 $4)      ; $7 = pixel pointer
-      (memset-8 $7 $3 $12)       ; draw row
-      (add-int $4 $4 $2)         ; next row (+= 640)
-      (sub-int $5 $5 $1)         ; decrement row count
-      (jump-gt-int &draw-box-outer $5 0))
-    (return)))
+      (add-int $27 $15 $5)     ; $27 = row end = current + width
+      (register-move $29 $15)   ; $7 = pixel pointer
+      (memset-8 $29 $2 $5)      ; draw row
+      (add-int $15 $15 $1)     ; next row (+= 640)
+      (sub-int $6 $6 $30)    ; decrement row count
+      (jump-gt-int &draw-box-outer $6 0))
+    (return nil)))
 (data
 	(label screen-namespace "/dev/screen/0")
   (label mouse-namespace "/dev/mouse/0")
diff --git a/test/paint.rom b/test/paint.rom
index 4f67b04..1d68daa 100644
Binary files a/test/paint.rom and b/test/paint.rom differ