diff --git a/cat.html b/cat.html
index fae64ca..b662ce6 100644
--- a/cat.html
+++ b/cat.html
@@ -1860,7 +1860,7 @@ console.log("lev " + lev + " newwid " + newwid + " ratio " + ratio);
                                                3,8,      5,8 ); 
 		this.addlevelgoals("food", 25);
 
-		this.addlevel(21, false); // oooooooooooo
+		this.addlevel(21, true);
 		this.addlevelallowedthings("curtain");
 		this.addlevelforcethings("curtain", 2);
 		this.addlevelgoals("curtain", 2);
@@ -4408,6 +4408,130 @@ console.log("lev " + lev + " newwid " + newwid + " ratio " + ratio);
 			drawtick(ctx, x, row2y, x + imgsize, row2y + imgsize, PATHLINECOLGOOD, 3);
 
 
+		} else if (curlevel == 21) {
+			var tempslashes;
+			cury = this.drawhelpsubtitle(ctx, "Curtains", cury);
+
+			ctx.textAlign = "left";
+			ctx.textBaseline = "bottom";
+			shadowtext(ctx, "Cats like climbing curtains.", HELPTEXTSIZE,helpcol, textxspace, cury); 
+			cury += HELPTEXTYSPACE;
+			cury += HELPTEXTYSPACE;
+			shadowtext(ctx, "Climb across curtains to swap places with", HELPTEXTSIZE,helpcol, textxspace, cury); 
+			cury += HELPTEXTYSPACE;
+			shadowtext(ctx, "anything on the other side.", HELPTEXTSIZE,helpcol, textxspace, cury); 
+			cury += HELPTEXTYSPACE;
+			shadowtext(ctx, "This also causes the curtains to become damaged.", HELPTEXTSIZE,helpcol, textxspace, cury); 
+			cury += HELPTEXTYSPACE;
+
+			cury += HELPTEXTYSPACE * 1.5;
+
+			// top line of curtain demo
+			x = imgsize;
+			y = cury;
+			row1y = y;	
+
+			ctx.drawImage(image['cat'], x, y, imgsize, imgsize);
+			linex[0] = x + imgsize/2; 
+			liney[0] = y + imgsize/2;
+			x += gridsize;
+
+			ctx.drawImage(image['curtain'], x, y, imgsize, imgsize);
+			x += gridsize;
+
+			ctx.drawImage(image['curtain'], x, y, imgsize, imgsize);
+			x += gridsize;
+
+			ctx.drawImage(image['cheese'], x, y, imgsize, imgsize);
+			linex[1] = x + imgsize/2; 
+			liney[1] = y + imgsize/2;
+			x += gridsize;
+
+			// line to show path
+			drawarrow(ctx, linex[0], liney[0], linex[1], liney[1], PATHLINECOLGOOD, LINEWIDTH, PATHARROWSIZE);
+
+			// arrow to middle
+			y = row1y + imgsize/2;
+		
+			x2 = x + gridsize*2;
+			y2 = row1y + imgsize/2;
+
+			drawarrow(ctx, x, y, x2, y2, "red", HELPLINEWIDTH, HELPARROWSIZE);
+
+			/////////////
+			x = x2 + 10;
+			y = y2 - imgsize/2;
+
+			ctx.drawImage(image['cheese'], x, y, imgsize, imgsize);
+			x += gridsize;
+
+			ctx.drawImage(image['curtainshred'], x, y, imgsize, imgsize);
+			x += gridsize;
+
+			ctx.drawImage(image['curtainshred'], x, y, imgsize, imgsize);
+			x += gridsize;
+
+			ctx.drawImage(image['catfull'], x, y, imgsize, imgsize);
+			x += gridsize;
+			// oooooooo swap lines
+
+			cury = y + gridsize;
+			cury += HELPTEXTYSPACE;
+			cury += HELPTEXTYSPACE;
+
+			shadowtext(ctx, "Climbing a damaged curtain will shred and destroy it!", HELPTEXTSIZE,helpcol, textxspace, cury); 
+			cury += HELPTEXTYSPACE;
+			cury += HELPTEXTYSPACE;
+
+
+			// top line of curtain blow up demo
+			x = imgsize;
+			y = cury;
+			row1y = y;	
+
+			ctx.drawImage(image['cat'], x, y, imgsize, imgsize);
+			linex[0] = x + imgsize/2; 
+			liney[0] = y + imgsize/2;
+			x += gridsize;
+
+			ctx.drawImage(image['curtainshred'], x, y, imgsize, imgsize);
+			x += gridsize;
+
+			ctx.drawImage(image['curtainshred'], x, y, imgsize, imgsize);
+			x += gridsize;
+
+			ctx.drawImage(image['cheese'], x, y, imgsize, imgsize);
+			linex[1] = x + imgsize/2; 
+			liney[1] = y + imgsize/2;
+			x += gridsize;
+
+			// line to show path
+			drawarrow(ctx, linex[0], liney[0], linex[1], liney[1], PATHLINECOLGOOD, LINEWIDTH, PATHARROWSIZE);
+
+			// arrow to middle
+			y = row1y + imgsize/2;
+		
+			x2 = x + gridsize*2;
+			y2 = row1y + imgsize/2;
+
+			drawarrow(ctx, x, y, x2, y2, "red", HELPLINEWIDTH, HELPARROWSIZE);
+
+			/////////////
+			x = x2 + 10;
+			y = y2 - imgsize/2;
+
+			ctx.drawImage(image['cheese'], x, y, imgsize, imgsize);
+			x += gridsize;
+
+			ctx.drawImage(image['pow'], x, y, imgsize, imgsize);
+			x += gridsize;
+
+			ctx.drawImage(image['pow'], x, y, imgsize, imgsize);
+			x += gridsize;
+
+			ctx.drawImage(image['catfull'], x, y, imgsize, imgsize);
+			x += gridsize;
+
 		}
 
 		ctx.textAlign = "center";
diff --git a/todo b/todo
index fcd158b..d8f215b 100644
--- a/todo
+++ b/todo
@@ -10,8 +10,6 @@ https://www.smashingmagazine.com/2012/10/design-your-own-mobile-game/
 -------------------
 
 
-*things shouldn't all if something is swapping to underneath them!.
-
 new door fell down on top of new goat!!
 	(or the other way around ??)
 	check code for doors falling when off the top of the screen.
@@ -23,10 +21,6 @@ change 'thing' to have a constructor!!
 
 
 curtain 
-	*normal chance for curtain (5%)
-	*allowing climbing over to curtain from any dir
-	*becomesleepy after climb
-	*curtain shred explosion
 	help (lev21)
 		cats can climb across curtains in any direction.
 
@@ -55,7 +49,6 @@ curtain
 
 
 remaining levels.
-	*19/20 - more with brick patterns
 	22/23/24 - curtains  (shred 2, 4, 6)
 	24/25/26 - boxes
 	26/27/28 - cat toys