Level 11 is the eleventh level of the Main Tunnel of Run 3. The colour has now changed, and will stay like this until Level 20.
If you chose the Skater in the last cutscene, this is a good practice level for him. If you chose the Runner, pause and pick the Skater. Using the Skater to navigate through this level is more easier than the Runner. Skater is much much faster than the Runner. Using him to leap over holes and gaps! Feel free to let him skate along the crumbling tiles! He is always fine!
Just be careful of jumping. Don't leap into holes, or you will fail.