Episode 4 of RainCloud SMP is the first of three videos called "Mob Sorter." Basket and Scoti_Garbidis already have a spawning platform in the sky. This time they start on what goes under it: a chute down from the platform, a room for mobs to land in, and water channels to push spiders off to one side. By the end the water is in and the lava is not.
Chicken jockeys and free glass
It opens with a shout: "Zombie chicken, zombie chicken! Just fell out of the thing!" In the finished design, they say, mobs will "track towards the villager" and "get burninated."
They need glass, and before going for sand they look around town. "We're only here on the server for a month." One stop has "glass for days," and they take some, leaving one block behind. On the way they sprint-jump along a stone bridge that has ice under it, which carries them a long way, and pass a hill with MOUNT BS on it. Ice under every block goes on a list of requests for the next server that invites them, with half-slab grass added, since the ice only helps under half slabs.
The chute
After a cut they are back with a slime block, and work moves under the iron platform. Redstone blocks go in, then a chute heads down about four blocks to a cobblestone floor. They go back and forth on the chute's size, settling on two by two. "The room that we're gonna be dropping them into is three by three on the floor. That's the main thing that matters." Wood comes from a tree they cut down nearby. "We're gonna be record label owners. We're gonna be bajillionaires."
Spider catchers
Next come the spider catchers, a floor one block lower beside the landing room. Will mobs spawn on the cobblestone? Not once water covers it. The first channel goes in three by three, then gets cut to two wide, "'cause they'll get pushed in," and from there into lava.
Filling it means a lot of climbing with buckets. "That'd be real easy if it was in creative." Signs hold the water back, and low spots catch spills "in case I do what I normally do, mess things up." Mobs start piling into each other ("This is real bad"), but one of them is sure they will sort themselves out: "Trust me."
A pit for lava
The water does pour out once, and a block has to come out so it turns the corner. The plan for spiders is a pit two blocks deeper with lava at the bottom: "that's where the spiders are gonna get sorted." Glass goes over it so they can watch.
Then a worry. Lava gives off light, and the pit sits near "our dark room." Nobody is sure. "We'll find out. We can always tweak this."
Where it ends
"Alright, so we need to get some lava." The episode stops there. After the end cards, a short tag plays on a snowy rooftop with a button. "If I hit this button and it blows up, we'll have it on record." Nothing happens. "Okay, that was fun. Science!"