Keep Zombies Off Boss Platform?

[sorcus]

Is there any way to prevent zombies from walking on to/spawning on my platforms that I built to do Eye of Cthulu?

[Super Nils]

nah, but NPC's and sources of light reduce enemy spawn ratio, plaze a lot of em

[zman9000]

sorta? if i remember right, player made, non-natural back walls prevent spawns?
i don't remember if it has to be apart of a structure, but if it does you could make the arena a giant room of you wanted to go completely crazy.

that might be the only way i can think of, assuming this is all correct/hasn't changed