It is also easily modified to get higher.
Step 1: Making a Scaffold
Part of the scaffold is left out, on the black rods around that there are dark grey connectors.
There is also a small ramp at the orange connectors, a yellow connector at the top, and extra base at the bottom, front.
Step 2: Moving Part
Step 3: Adding That
Step 4: Parts of the Top Side
Make 1 of the first part, 5 of the second part, six of the third part, and ten of the fourth part.
Step 5: Connecting the First 3 Parts of the Previous Step
Step 6: Assembling the Top Bit
Step 7: Entrance Pieces
Step 8: Assembling Entrance #1
Step 9: Assembling Entrance #2
Step 10: Adding the Entrance
Well almost. Just make sure that you count 6 connections.
Step 11: Motor Parts
Step 12: Putting the Motor Bits Together
Step 13: Add That, and You're Done!
That was easy (or at least, to me).