• A parkour-tastic course with plenty of deadly pitfalls for your player.

• The use of Border, Allow & Deny Blocks to keep your player from gaming the system.

• A goal so your player knows when he / she has won.

General hints:

• The Nether is a great place to build a 3d Platformer

• Flat worlds are also great because once you build your course, you can easily use code to delete the ground.