I was digging underground in Terraria and when I was mining some stone, I noticed they had red spots on them called Active Stone Blocks. When I had it in my characters hand, there were red lines starting to go down the tunnel I was going down through. What are these red lines?
I'm a beginner of Terraria, so I don't know much about this.
Those red lines are wire, which is used to connect triggers and mechanisms. Wire is invisible unless you're holding something that can interact with it, like the Active Stone Block, which becomes non-solid when activated by wire. In the underground, you will usually find it connecting pressure plates to various traps. You can check the wiki for more information.
Sometimes they hold boulders, and when you're underneath the trap, the active block moves, and it drops the boulder. I'm guessing you dug through a boulder trap.
