So im a bit new to minecraft or at least after basics. I'm building a mob farm in the sky and I had this idea of making a giant room with two blocks wide hole in the floor that is very deep and in the end there is hopper where all of the mobs land and eventually i come and kill them and the drop is gathered in a chest underneath the hoppers.
However i found two flaws in my build after i had completed it.
The first one is because my idea involved a water stream inside the giant room pushing everything towards the hole. But I can't calculate where to put the water and it became a pain to get rid of all the water with lava because i messed up that much. Is there any website or something that could help me calculate this? or is there a better idea you guys might have that doesn't involve many expensive stuff to make my build work. I am thinking of putting a villager on top of the holes but i really don't want to do unless im certain that it will work so let me know what you think.
The second issue is if I find a solution to the first issue, should i make it an automatic farm or an exp farm? im not sure which one to choose.
the dimensions of the farm i made:
30 x 15
H = 7
The hole is not in the middle however and the farm is in the sky.
Most mobs won't spawn in water so you need some way to turn the water on and off.
I'm not sure what you want to do with the villagers unless it's to attract zombies, that would work and open trapdoors would make the zombies think they can walk on them so they walk into the hole, but it would only work for zombies and drowned and drowned would probably be able to kill the villagers eventually by throwing tridents.
A 2X2 hole may not be big enough for spiders to reliably fall through without grabbing the edge.
The best way to achieve what you want would be have water sources along the wall that are released by trapdoors or in a dispenser on a redstone timer. This would allow the mobs to spawn in the dark and then every so often get flushed to the opening where they fall down to a killing chamber. Mob farms like this one are usually used as drop farms because of the variety of mobs that spawn.