It’s meant to be played on graph paper. The general idea is a randomly generated dungeon crawl. When you get to a door, you roll 1d6 and draw the next room! Each M is a monster, and each L is loot, which also has random tables to determine what is what, or you could use random tables from any other system with the general idea.
I love the approach of having “hard coded” rooms that happen at certain intervals. I wish I would have had this a few weeks ago when my group was exploring a cave system. I love that d20 table. I may use that for the game I’m running with my kids that is (of course) set in the Minecraft world 😄