I know this has been done plenty with command blocks before, but I wanted to try something simple for my first function creation. This uses the new function feature in 1.12 to add 7 traps in vanilla Minecraft.

To install, first you need to download the folder here called greystalk. Then create a new world (or use and existing one) and go into your .minecraft folder. Go into your world saves, open the world you want to use, go into data and then functions, paste the greystalk folder there, and you're basically done. Go back ingame into your world and run these two commands.

/reload
/gamerule gameLoopFunction greystalk:loop

Then you should be given a book explaining how the traps work, and everything should be ready.

You should know that the traps do not work on mobs, only players. As a result, it should be multiplayer compatible.

Let me know if you have any questions or bug reports.