The knobs

How a game feels is a few dozen numbers, and this page says where each of them is. All of it is data on const classes, so changing one is a recompile and never a schema change, and none of it needs a renderer to test.

Where the numbers are #

Movement #

MovementSettings is what every body in every genre stands on, player and monster alike.

const MovementSettings(
  walkSpeed: 6.0,            // sprintSpeed is 10.0
  groundAcceleration: 70.0,  // how fast it reaches that speed
  groundFriction: 55.0,      // and how fast it stops
  airAcceleration: 14.0,     // control in the air, deliberately much lower
  gravity: 24.0,             // 9.81 feels like a documentary
  jumpSpeed: 8.0,            // straight up, meters per second
  stepHeight: 0.4,           // a kerb it walks over instead of into
  coyote: Duration(milliseconds: 100),     // a jump still counts this long after a ledge
  jumpBuffer: Duration(milliseconds: 100), // and this long before landing
);

The two forgiveness windows at the end are the ones a player feels and cannot name. Set both to Duration.zero and the game plays as if it were fighting you, with nothing on screen having changed.

What a platformer adds on top #

RunnerSettings is the second layer, and it is large because a platformer is a verb list. A sample of it, with the shipped defaults:

Weapons and monsters #

A weapon is a WeaponDef, and a game's arsenal is a list of them. The five it insists on are name, behaviour, ammo, damage and shotsPerSecond; everything else has a default that means "the simple case".

The shipped shotgun, from flutter3d_game_shooter's sample arsenal:

import 'package:flutter3d_game_shooter/flutter3d_game_shooter.dart';

const WeaponDef(
  name: 'Shotgun',
  behavior: HitscanBehavior(),   // or MeleeBehavior, or ProjectileBehavior
  ammo: AmmoType.shells,
  damage: 11.0,                    // per ray
  shotsPerSecond: 1.4,
  rayCount: 8,                     // what makes it a shotgun
  spread: 0.10,                    // radians
  range: 60.0,
  falloffStart: 6.0,               // full damage to here
  falloffEnd: 26.0,                // and a floor of minimumDamageFraction past here
  minimumDamageFraction: 0.2,
  knockback: 2.0,
  recoil: 0.05,
  recoilRecovery: 4.5,
  loudness: 28.0,
);

loudness is the one to know about: firing is a noise with a radius in metres, and it is what wakes the room next door. A quiet weapon is a design decision, not an audio setting.

AmmoType.none exists so a starting weapon can never run out. A player stranded with nothing to fire is a player reloading a save.

A monster is a MonsterDef: health, speed, attack, radius, height, and then sightRange (26 m), turnRate (6.0 rad/s), painChance (1.0) and painCooldownSeconds (0.2). The last two are what make a heavy monster feel heavy: a painChance under one means some hits do not interrupt it, and it keeps walking at you.

The catalogue is handed to Bestiary rather than reached for, so a second shooter brings its own and inherits none of this one's.

Cars #

VehicleSettings is a car, and TireSet is what it is standing on. The engine numbers are the obvious half:

Those last three are a repaired bug rather than a feature: the circuit's starting grid sits on a one-in-fifty rise, and a car with no rolling resistance and no static hold rolled backwards off it, gaining speed, from the moment the level loaded. holdSlope is what stops the fix becoming a handbrake that is always on.

Grip lives in TireSet instead, and TireSet.road is the shipped set. That split is deliberate: a wet race is the same car with different tyres.

Difficulty, as a number #

AiSettings.skill is 1.0, and it scales the rest. Under it sit the numbers that decide how a driver is fast: brakeHorizon (45 m of lookahead for a corner), corneringGrip (14.0, how much the driver believes the car has), lookAheadPerSpeed (0.55) and rubberBandClamp (0.22, the ceiling on catching up).

The picture #

RenderSettings holds the look, and most of it is off by default because most of it costs. exposure is 1.6 and tonemap is on; bloom, fog, look (contrast, saturation, temperature, vignette, grain) and sky are each their own settings object. reflections and ambientOcclusion both default to enabled: false.

Everything 0.8.0 added is off as well, and each one says what switching it on costs:

AdaptiveQuality sits outside RenderSettings and rewrites it each frame. AdaptiveQualitySettings.budget is 16 667 µs, sixty frames a second; a row is kept while it fits under headroom (0.9) of that and climbed to only after it has fitted under climbHeadroom (0.75) for climbFrames (30) frames running. The rows come from QualityTable.of(deviceClass), and the costs in the tables committed today are software-rasteriser stand-ins until each device class is measured. The frame has the rest.

ShadowSettings is where the two expensive numbers are:

• resolution (1024) is the directional light's map, split into cascades (3) tiles.
• cubeResolution (512) is the atlas point and spot lights share, six faces across and one row per shadowed light.

Changing them honestly #

Every class on this page is reachable from a plain test() with no window and no GPU, because the packages they live in import no renderer. That is the difference between tuning and guessing: a jump height that has to clear a specific ledge, an AI lap that has to come in under a time, a car that has to still be on the grid after ten seconds. Each is a test that runs in milliseconds and says what happened, where a playthrough shows you a frame and leaves you to judge it.

Testing is how this repository does that, and the racing package's test/parked_test.dart is a short worked example of a feel bug caught that way.