You can draw static or dynamic boxes with the mouse  which alters the current level.   It’s as simple as I could make it, but once I add quick undo button and a way to define the spritesheet region, I’ll be ready to work on the player and game conditions.  It’s looking like the gameplay will be swimming to the exit.  The levels will use the dynamic boxes as obstacles in a maze, so you might need to use a lever or push blocks to reach the goal.