feellab-mcp

Feel Lab

An FPS feel checklist, measured: every interaction a player has, checked from what the game really did.

Game feel is what a player feels between pressing a key and seeing the world answer. A shot should flash, sound and kick on the same frame; a round striking a wall should throw dust, make a sound and leave a hole; a hit taken should jerk the view and show where it came from; a blast nearby should shake the screen more than one far away. When one answer is missing or late, the game feels floaty or cheap, and nobody can say why.

Feel Lab turns that into checks. Your game's probe plays standard scenes and writes a timeline: the camera every frame, and every sound, effect, mark and damage event with its time. Feel Lab measures latency, kick, shake, presence, match and smoothness from it, and judges each item of an 82-item checklist. It never runs your game: any engine can write the timeline (docs/TIMELINE.md).

The checklist

Group	Items	Measured from a timeline
A. Shooting (your own gun)	19	9
B. Hitting (your bullets land)	15	6
C. Getting hit (damage taken)	9	4
D. Movement and the body	11	2
E. Interacting with the world	7	0
F. Enemies (zombies)	5	0
G. Explosions, fire and the world	5	1
H. Sound mix	4	0
I. Screen and comfort	4	0
J. Smoothness (feel breaks when the frame does)	3	1

Items no timeline can show (a colour-blind option, a reload cancel's timing) are left for a person, with what to look for. feellab checklist prints them all.

What it measures

Measure	Example
Latency	the shot's flash and sound on the shot's frame; the hit marker within 50 ms of the hit
Sync	the shot's sound within 45 ms of its flash (ITU-R BT.1359)
Kick	the camera turns at least 0.3 degrees on a burst and settles within 0.6 s
Shake	a blast 5 m away shakes the view; one 50 m away at least 3 times less
Presence	every impact has an effect, a sound and a mark; every round fired ejects a case
Rhythm	footsteps at walking cadence (about 100 steps a minute and up); the head bobs
Smoothness	no frame twice the median length round a shot or a blast

Every rule names its source. A range from game practice rather than evidence is marked as an estimate.

Try it

pip install feellab-mcp
feellab demo demo
feellab judge demo

The demo writes timelines for two made-up games: "Juicy" passes every measured item; "Bare" (a debug dot where a round lands, no shake, silent steps) fails 17.

Use it in your game

• Have your probe play the scenes in src/feellab/data/scenes.json and write one timeline each (docs/TIMELINE.md). Wrap the calls that start sounds and effects so each is recorded with its time; note the moments with no sound or effect of their own (a shot, an impact, a hit marker, damage, a flinch).
• Record a camera frame before the scene's cause (a shot, a hit, a blast): kick and flinch are measured from it.
• Tag what you can ("tags": ["muzzle"]). Where your asset names do not say what a sound or effect is for, put a feel_rules.json beside the timelines: {"dry": "slidelock"} tells Feel Lab that a sound named after a slide lock is the click of an empty gun.
• feellab judge <folder>, or gate_rows for a gate.

The first game to use it (ToangTown) found 52 failing cases on four guns: a debug dot where a round lands, no shake anywhere, no blood, no footsteps, a climb that never comes back, a stall on the first shot.

Tools

Tool	What it does
list_checklist	The checklist by group: what the player should get, measured or for a person.
list_scenes	The standard scenes a probe plays.
list_metrics	Every metric: scene, unit, rule and source.
check_timeline	A timeline file against the contract.
judge_folder	A folder of timelines judged: each item's values and verdict, and a Markdown report.
gate_rows	The metrics as rows for a gate (Weapon Lab's row format).

{"mcpServers": {"feellab": {"command": "feellab-mcp"}}}

FEELLAB_OUT is the only folder Feel Lab writes to (its reports); ~/.feellab by default.

Where it came from

Feel Lab was built for ToangTown, an Unreal 5.8 co-op zombie FPS, next to Weapon Lab (weaponlab-mcp), whose Gate can judge Feel Lab's rows as cases.

License

MIT