Small snow golem creeper farm

Small creeper farm run by snow golems, with no cats and no redstone. Creepers spawn on a platform, three snow golems penned in the middle knock them off the edge with snowballs, and they land on soul campfires below. Slabs and a ring of torches around the outside are what stop anything else spawning in range. It is by far the cheapest creeper farm here at 433 building blocks, and it stacks by using the roof of one layer as the floor of the next. It cannot go in a hot biome, the snow golems melt in savanna and desert. Java is what it was built for, but unusually for this kind of farm, Bedrock builders report it working too with the AFK platform much lower.

If creepers stop spawning on newer Java versions, move the AFK platform down to about 105 to 110 blocks above the farm. That is the single most upvoted comment on the video.
Do not build it in a hot biome. Snow golems melt in savanna and desert, and two builders had to tear the whole thing down and start over.
Spiders spawn on the buttons and kill the snow golems. Swapping those buttons for slabs fixes it.
Put a button on the block the snow golems sit on, so zombies cannot spawn inside the pen with them.
On 26.2 the soul campfires can light nearby spawnable blocks to level 1 or 2. Moving the campfire and hopper setup down two blocks brings the rate back.
On Bedrock put the AFK platform about 20 to 22 blocks above the spawn chambers instead, because mobs there do not spawn past 44 blocks.