The towers on the east core cover all directions while still being able to shoot at enemies at the wall.
Make sure the physical wall (3DU) covers the path completely. The magic blockade is in the middle of the path.
Start W17 and use first wave to upgrade beams, auras, traps and the east fireballs.
For W18 switch to your summoners. I use 2 boost summoners on the west towers and 1 auto-repair summoner to upgrade.
Restart after W24 for highest ult/h rate. (According to 50 runs for data)
this is basically catbugs build so credit to him.
20.03.2022: some changes to help with stability of this build.