The spiders is supposely not able to climb sandstone, but can climb fences, making them pretty useless. And spiders shouldn't be able to climb vertical on glass, make no sense for them to do so.
Entity: usually, my next step after getting the basics is digging a staircase or vertical shaft with a ladder down to bedrock, going up a few blocks and then doing some grid mining. I typically build a main tunnel about 40 blocks long with side branches every 4th block, I extend those side tunnels 20 blocks. It's a good…