Pretty cool smaller dungeon! Totally free, quick, and nice quality. :)
Did the walls, doors, stairs using GridMapper, then used Microsoft Paint for text and numbering, and also to shade the solid areas gray. I hadn't known that the Paint 'fill by color' feature (paint bucket icon) could be used to fill selected grid squares until today, and it worked out pretty well, I think! Using a number of colors might be a cool way to designate special features, pools, lava, etc.
This is for an adventure I may never finish, most of it is written but not edited, so if you're wondering,"Where the hell is the entrance?", room #1 is shaped like a pyramid; the four walls slope steeply upward to converge at a 10x10' apex which is an opening to the surface. It is a 60' vertical drop from the entry to the floor of the chamber. The Primordial Ones simply fly/levitate in and out like hornets from the hive, but the Party may find entry (and exit!) more difficult! Plenty of space to add in a staircase, if you like... or use the entire thing as a sub-level below a pit trap!