Games like THE XEN
Games like THE XEN include Portal, Monument Valley 2, Zuma Deluxe, Children of the Sun, and Defy Gravity Extended. We matched them by the tags players give THE XEN on Steam (Strategy, Puzzle, Arcade, Psychological Horror, and Puzzle Platformer): closest matches first, and among equally close ones the better-known games.

Portal
Shared: Puzzle · Puzzle Platformer · Action

Monument Valley 2
Shared: Strategy · Puzzle · Action

Zuma Deluxe
Shared: Puzzle · Arcade · Strategy

Children of the Sun
Shared: Strategy · Arcade · Action

Defy Gravity Extended
Shared: Puzzle · Puzzle Platformer · Action

Zup!
Shared: Puzzle · Casual · Puzzle Platformer

Buckshot Roulette
Shared: Strategy · Horror · Psychological Horror

In Sound Mind
Shared: Puzzle · Psychological Horror · Action

Little Nightmares
Shared: Puzzle · Puzzle Platformer · Horror

Pacify
Shared: Psychological Horror · Horror · Strategy

Firework
Shared: Puzzle · Psychological Horror · Horror

UFO 50
Shared: Strategy · Arcade · Action

Little Nightmares II
Shared: Puzzle · Psychological Horror · Horror

Waveform
Shared: Puzzle · Strategy · Arcade

Nubby's Number Factory
Shared: Strategy · Arcade · Psychological Horror

LIMBO
Shared: Puzzle · Puzzle Platformer · Indie

Poppy Playtime
Shared: Puzzle · Psychological Horror · Horror

PAC-MAN™ Championship Edition DX+
Shared: Arcade · Action · Score Attack

Shipwrecked 64
Shared: Puzzle · Psychological Horror · Strategy

ISLANDERS
Shared: Strategy · Puzzle · Indie

Death and Taxes
Shared: Strategy · Psychological Horror · Puzzle

Portal 2
Shared: Puzzle · Puzzle Platformer · Action

The Ball
Shared: Puzzle · Strategy · Puzzle Platformer

Planet of Lana
Shared: Puzzle Platformer · Action · Puzzle