PCGame

M.A.S.S. Builder

Mech action RPG about building suits to fight alien hordes

Vermillion Digital · Published by Sekai Project · Released Sep 14, 2025

ActionIndieRPGStrategy

Reviews
Very Positive
86% of 3,882
Recent reviews
Mixed
50% of 12 in 30 days
Players
14
daily peak, Nov 7, 2026
Steam Deck
Playable
Last update on Steam
1 year ago
Sep 21, 2025
Minimum PC
GeForce GTX 1050
8 GB RAM · 3 GB disk
Full requirements

What is M.A.S.S. Builder?

An action RPG set in a future where alien beasts have driven humanity into shelters. You command a private military company, customize a mech and its weapons, and use boosters to move through battles against hordes of Quarks and larger enemies. Armor appearance and combat stats are customized separately.

For you if...

  • +you like customizing mechs down to small visual details
  • +you enjoy fighting hordes with a mech you designed

Not for you if...

  • −you want a story-focused campaign more than mech building

What players say

86% of 3,882 reviews are positive · 50% of 12 in the last 30 days

Players praise the range of options for customizing mech and weapon appearances. Many say the combat feels clunky and repetitive, with ranged weapons weaker than melee, and some find unlocking parts grind-heavy.

Screenshots and trailer

M.A.S.S. Builder screenshot 1

M.A.S.S. Builder system requirements

Minimum: GeForce GTX 1050, 8 GB RAM, 3 GB of disk space.

As published by the developer.

Can my PC run M.A.S.S. Builder?

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Minimum

OS
Windows 7, Windows 8.1, Windows 10 (64-bit versions only)
Processor
Intel Core i5 or better / AMD Phenom II X3 or better
Graphics
NVIDIA GeForce GTX 1050 or better / AMD Radeon RX 560 or better
Memory
8 GB RAM
Storage
3 GB available space

Recommended

Requires a 64-bit processor and operating system

Does M.A.S.S. Builder have co-op or multiplayer?

Yes: co-op online. It also has a single-player mode.

Does M.A.S.S. Builder run on Steam Deck?

Playable Playable: it runs on Steam Deck with some adjustments.

  • The launcher or setup tool may need the touchscreen or virtual keyboard
  • Some text entry requires manually opening the on-screen keyboard
  • All functionality is accessible with the default controller configuration
  • Shows Steam Deck controller icons
  • In-game text is legible on Steam Deck
  • Default graphics settings perform well on Steam Deck

PC version details

DRM
None declared on Steam
Controller
Full controller support
Platforms
Windows
Steam features
Cloud saves, Family Sharing
Languages
Text only: English, Japanese, Simplified Chinese, Thai, Traditional Chinese.

Does M.A.S.S. Builder use AI-generated content?

No AI-generated content is disclosed on the game's Steam page.

Self-reported by the developer under Steam rules: it covers AI content that ships in the game, not tools used to make it. Steam page checked on Oct 25, 2026. How to filter AI games on Steam

Tags

Recent updates

1 DLC available.

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