Phobos

Clear the demons to prove you're human. A Caputchin first-party game that drops the visitor into a real, first-person DOOM arena: true 3D, the iconic shotgun, and demons closing in.

License: Phobos is GPL-2.0-only (it links the open-source DOOM engine). Embedding it through the standard check does not place your own site under the GPL. See Licensing.

How it plays

You spawn in the middle of a demon-infested arena, shotgun in hand. Move, turn, and fire to clear the wave. It is the genuine DOOM feel: 3D rooms with a raised platform and varied tech-base walls, charging imps and pinkies, the heads-up display, and DOOM's classic auto-aim (line a demon up horizontally and the shot lands, no precise vertical aiming). Kill the target number of demons and the round is Verified - then keep playing as long as you like.

Every round is different. The demons are placed fresh from a one-time secret the server issues for that attempt, so no two challenges are the same and a layout you have seen before will not come back.

Why it's a strong check

The score is never taken on trust. When you finish, the server re-plays your actual run inside a sandboxed copy of the same DOOM sim and accepts only the result it recomputes. A bot cannot post a fake "I won" - it has to produce an input that genuinely clears the arena. And because the demons are positioned from that per-attempt secret, a pre-recorded playthrough fails: the monsters are somewhere else, so the recorded shots miss.

Customization

Everything is driven by caputchin.json and resolved by the widget per site:

• Difficulty - kills required to pass, DOOM skill (1-5), how many demons spawn, fast monsters, respawning monsters, which arena, and an optional time limit. The challenge can be as quick or as punishing as the site wants.
• Locales - all on-screen text (start screen, controls hint, Verified badge) ships in the 11 official languages and is fully overridable.
• Skins - light and dark chrome presets the host picks; colors for the background, HUD, buttons, and the Verified badge.

Accessibility and support

• Keyboard and touch: full WASD / arrow-key play on desktop, and a large on-screen control pad with fire on mobile (multi-touch, so you can turn and fire together).
• Fixed size: a fixed 16:10 view (native 640x400). It scales down to fit a narrower embed but always keeps that aspect ratio and never exceeds its native size; it does not reflow, so it is not a responsive layout. Give it room.
• Sound: short SFX (shots, demons, doors) with an on-screen mute toggle, so audio is optional and off-by-a-tap.
• Phobos is a fast visual shooter, so it is not screen-reader solvable - sites that need a non-visual challenge should pair it with an accessible alternative.

Add it to your site

Phobos runs as a sandboxed widget behind a Caputchin verification check. Preview it live and copy the embed snippet, with your locale, skin, and difficulty presets, from its marketplace listing.

Licensing

Phobos links the open-source DOOM engine, which is GPL-licensed, so the game is GPL-2.0-only.

What this means if you embed Phobos:

• Your site is unaffected. Phobos runs in Caputchin's sandboxed iframe, so the standard check does not place your site under the GPL.
• Caputchin carries the obligation. As the distributor, Caputchin publishes the complete corresponding source (the engine included) in this package's engine/ directory.
• Re-hosting is the exception. If you download and serve the Phobos bundle yourself, you become the distributor and take on the GPL-2.0 obligations directly.

The game ships with no warranty, as stated in the GPL. The full license text is in LICENSE, with engine and game-data attribution in THIRD-PARTY-NOTICES.md.

DOOM is a trademark of id Software LLC; Phobos is not affiliated with or endorsed by id Software, ZeniMax, or Microsoft. It is built on the open-source DOOM engine and free, libre Freedoom game data - no id artwork or game files. See TRADEMARK.md and THIRD-PARTY-NOTICES.md.