The entrance to R-Maze is randomly selected from one of 50 locations upon starting a new save.
#1: Red Sands B
#2: Blue Flow
#3: Retro Dungeon
#4: White Shores
#5: Above the Clouds
#6: Puzzle Chamber
#7: Owl Swamp
#8: Micro World
#9: Sands of Time
#10: Red Sands A
#11: Pink Snowscape
#12: The Depths
#13: Flesh n' Blood
#14: Unicorn Woods
#15: Undersea Expanse
#16: Dark Stairways
#17: Windy Canyon
#18: Occult Basement
#19: Lower Totem Hill
#20: SUGAR
#21: Isle of Seasons
#22: Tree Trunk Complex
#23: Projector Room
#24: Swimming Pool
#25: Overgrown Rust
#26: Lamp World
#27: Black Waters
#28: Neon Zone
#29: Rainforest Road
#30: Decrepit Facility
#31: Another White
#32: Flower Field
#33: Particle World
#34: Chicago
#35: Yin Yang Lake (light version)
#36: Yin Yang Lake (dark version)
#37: Block Galaxy
#38: Thorny Vine World
#39: Mushroom Cathedral
#40: Jarred Rose
#41: Greenhouse
#42: Weird Forest
#43: Glowing Meadow
#44: Monochrome Building
#45: Sunset Cliff
#46: Succubus Grotto
#47: Sheet Music
#48: Orange Mausoleum
#49: Pink Block Sea
#50: Reverse Space Station (Appears to be bugged and does not show up in-game.)
