Games like 31st prototype
Games like 31st prototype include Machinarium, Sanfu, The Tiny Bang Story, Gorogoa, and Firework. We matched them by the tags players give 31st prototype on Steam (Puzzle, Hand-drawn, Old School, Robots, and Stylized): closest matches first, and among equally close ones the better-known games.

Machinarium
Shared: Puzzle · Hand-drawn · Steampunk

Sanfu
Shared: Puzzle · Hand-drawn · Mystery

The Tiny Bang Story
Shared: Puzzle · Steampunk · Hand-drawn

Gorogoa
Shared: Puzzle · Hand-drawn · Stylized

Firework
Shared: Puzzle · Mystery · Old School

Creaks
Shared: Puzzle · Hand-drawn · Stylized

Murders on the Yangtze River
Shared: Puzzle · Adventure · Exploration

Stray
Shared: Adventure · Puzzle · Robots

Chants of Sennaar
Shared: Puzzle · Adventure · Stylized

Slice of Sea
Shared: Puzzle · Hand-drawn · Adventure

COCOON
Shared: Puzzle · Adventure · Exploration

Storyteller
Shared: Puzzle · Hand-drawn · Adventure

Blue Prince
Shared: Puzzle · Exploration · Mystery

Syberia: The World Before
Shared: Puzzle · Steampunk · Adventure

Outer Wilds
Shared: Puzzle · Exploration · Adventure

Carto
Shared: Puzzle · Hand-drawn · Exploration

Lorelei and the Laser Eyes
Shared: Puzzle · Adventure · Exploration

The Great Ace Attorney Chronicles
Shared: Adventure · Steampunk · Visual Novel

The Death Game Report
Shared: Puzzle · Adventure · Mystery

Pentiment
Shared: Hand-drawn · Adventure · Stylized

The Room 4: Old Sins
Shared: Puzzle · Adventure · Mystery

Submachine: Legacy
Shared: Puzzle · Hand-drawn · Adventure

Quern - Undying Thoughts
Shared: Puzzle · Adventure · Mystery

ANIMAL WELL
Shared: Puzzle · Exploration · Adventure