modified plan.txt

plan.txt

@@ -25,7 +25,7 @@ other challenges:
 levels: which things are introduced in which level
 	DONE tutorial: flying demon, checkpoints, static, fire demon
 	DONE 1: platform moving horizontally, ladders
-	2: tilted platforms, platform moving vertically
+	DONE 2: tilted platforms, platform moving vertically
 	3: horiztonal demon, tack shooter
 	4: flipping triangle
 	5: spinning moving platform, staggered tack shooters