diff --git a/one_line_canvas.tal b/one_line_canvas.tal
index 6b3f308..724872a 100644
--- a/one_line_canvas.tal
+++ b/one_line_canvas.tal
@@ -8,39 +8,66 @@
 |58 @canvas-width
 |1f @canvas-height
 
+( zero page vars )
+|00
+@x $2
+@y $2
+
 (to run gui: `./run_ui.sh one_line_canvas.tal`)
 (to run debugger: `../uxn/bin/uxnasm one_line_canvas.tal one_line_canvas.rom && ../uxn/bin/uxnemu ../beetbug.rom ./one_line_canvas.rom`)
 %dbug  { #01 .System/debug DEO }
 %PX { #01 .Screen/pixel DEO }
-%ADD1 { #01 ADD }
 
 |0100
 @on-reset
 	setup-gui
 	( draw canvas bounds )
-	.canvas-width ADD1 .canvas-width ADD1 .canvas-height ADD1 draw-h-line
-	.canvas-width ADD1 .canvas-width ADD1 .canvas-height ADD1 #02 MUL draw-h-line
-	.canvas-height ADD1 .canvas-width ADD1 .canvas-height ADD1 draw-v-line
-	.canvas-height ADD1 .canvas-width ADD1 #02 MUL .canvas-height ADD1 draw-v-line
+	( top line )
+	.canvas-width #01 ADD .canvas-width .canvas-height #01 SUB draw-h-line
+    ( bot line )
+	.canvas-width #01 ADD .canvas-width .canvas-height #02 MUL #01 ADD draw-h-line
+	( left line )
+	.canvas-height #01 ADD .canvas-width #01 SUB .canvas-height  draw-v-line
+	( right line )
+	.canvas-height #01 ADD .canvas-width #02 MUL #01 ADD .canvas-height draw-v-line
 	;on-mouse .Mouse/vector DEO2
 	BRK
 
+@add-px-to-drawing
+    ( figure out if px on on canvas )
+    ( x too small )
+    LIT2 =canvas-width .x LDZ2 GTH2 ?/end
+    ( x too big )
+    LIT2 =canvas-width #0002 MUL2 .x LDZ2 LTH2 ?/end
+    ( y too small )
+    LIT2 =canvas-height .y LDZ2 GTH2 ?/end
+    ( y too big )
+    LIT2 =canvas-height #0002 MUL2 .y LDZ2 LTH2 ?/end
+    ( draw px to screen )
+    .x LDZ2 .Screen/x DEO2
+	.y LDZ2 .Screen/y DEO2
+	#01 .Screen/pixel DEO
+	&end
+	JMP2r
+
 @on-mouse ( -> )
-	.Mouse/x DEI2
-	.Mouse/y DEI2
+	.Mouse/x DEI2 .x STZ2
+	.Mouse/y DEI2 .y STZ2
 	draw-cursor
+	add-px-to-drawing
 	BRK
 
-@draw-cursor ( x* y* )
+@draw-cursor
 	( clear fg )
 	LIT2 0000 .Screen/x DEO2
 	LIT2 0000 .Screen/y DEO2
 	#c0 .Screen/pixel DEO
 	( draw cursor sprite to fg )
-	.Screen/y DEO2 ( x* )
-    .Screen/x DEO2 ( )
+	.x LDZ2 .Screen/x DEO2
+	.y LDZ2 .Screen/y DEO2
 	;cursor-sprite .Screen/addr DEO2
 	#41 .Screen/sprite DEO
+	JMP2r
 
 @draw-v-line ( l x y )
     SWP ( l y x )