1. Check out how many Force Area objects are used. In some areas, I wanted to restrict the player to a 2D plane only, but in others I wanted them to be able to go a block or two deep into the background. So instead of just using one big 2D plane, I cut it up into several sections to make sure players could reach the correct areas.
 
2. The hidden puzzle room (in the far right corner, under the final ladder) is a nice case study for triggers and moving platforms. You step on two "pressure plates", which are essentially just moving platforms that drop down when you touch them to reveal an invisible area trigger, which in turn sets off the flying wooden discs that push the soccer ball around. I modified this puzzle a lot to prevent glitches, such as the moving platforms pushing the ball through the wall or off the course...that's why the moving platforms rise from the floor and slide into the background, instead of just going up and down.

3.Shift + WASD (fast pan) and Shift + Q/E (10 floor jump) were the best shortcuts ever with this level, which required a lot of bouncing around between sections.
 
4. There are a lot of invisible info stickers attached to timer triggers. Instead of having the same info sticker message show up over and over again when you entered an area, I had it set to only show up once for 5 seconds or so. This helped it feel a little less repetitive and not feel out of place (like a hint about bombing a block showing up even after you've already blown it up).
 
5. I tried to squeeze every ounce of performance I could in the level, so I used area triggers to spawn enemies, move platforms, and light torches only when you've entered that particular section. The level has to keep track of all "interactive" objects that move around at all times, even if they're off screen, so it's helpful to have these guys hidden until they're really needed. A little extra boring grunt work, but hopefully it helps the level play a little smoother.