// In a Scene's create() method:

// --- Group: logical collection, no transform, great for pooling ---
const enemies = this.add.group();
enemies.create(100, 200, 'enemy');       // creates Sprite at (100,200)
enemies.create(300, 200, 'enemy');

// --- Container: visual parent with inherited transform ---
const hud = this.add.container(10, 10);
const icon = this.add.image(0, 0, 'heart');
const label = this.add.text(20, 0, 'x3');
hud.add([icon, label]);                  // children move/scale/rotate with hud

// --- Layer: render-ordering bucket, no position/scale ---
const bgLayer = this.add.layer();
const fgLayer = this.add.layer();
bgLayer.add(this.add.image(400, 300, 'sky'));
fgLayer.add(this.add.sprite(400, 300, 'player'));

// Empty group, add existing objects
const gems = this.add.group();
gems.add(existingSprite);
gems.addMultiple([sprite1, sprite2, sprite3]);

// Group with config -- creates children automatically
const coins = this.add.group({
    classType: Phaser.GameObjects.Sprite,
    key: 'coin',
    quantity: 10,           // overrides frameQuantity
    setXY: { x: 50, y: 300, stepX: 60 },
    setScale: { x: 0.5, y: 0.5 }
});

// Custom class type with pool limit
const bullets = this.add.group({
    classType: Bullet,       // must accept (scene, x, y, key, frame)
    maxSize: 30,
    defaultKey: 'bullet',
    runChildUpdate: true     // calls child.update() each frame
});

// Setup pool
const bullets = this.add.group({
    classType: Phaser.GameObjects.Sprite,
    defaultKey: 'bullet',
    maxSize: 30
});

// Fire a bullet -- get() finds first inactive member or creates one
function fireBullet(x, y) {
    const bullet = bullets.get(x, y);

    if (bullet) {
        bullet.setActive(true);
        bullet.setVisible(true);
        bullet.body.velocity.y = -300;   // if physics enabled
    }
}

// Deactivate when off-screen or on hit
function killBullet(bullet) {
    bullets.killAndHide(bullet);         // sets active=false, visible=false
    // If using physics, also reset the body:
    // bullet.body.stop();
}

// Alternative: manual getFirst
const inactive = bullets.getFirst(false);     // first where active===false
const active = bullets.getFirstAlive();       // first where active===true
const dead = bullets.getFirstDead(true, x, y); // first inactive, create if null

// Arcade Physics group -- every member gets a dynamic body
const enemies = this.physics.add.group({
    key: 'enemy',
    quantity: 5,
    setXY: { x: 100, y: 100, stepX: 80 }
});

// Static physics group -- immovable bodies
const platforms = this.physics.add.staticGroup();
platforms.create(400, 568, 'ground');

// Collide physics groups with each other
this.physics.add.collider(player, platforms);
this.physics.add.overlap(bullets, enemies, onHit);

// HUD that follows camera
const hud = this.add.container(10, 10);
hud.setScrollFactor(0);     // pinned to camera

const healthBar = this.add.rectangle(0, 0, 200, 20, 0x00ff00);
const healthText = this.add.text(210, -5, '100 HP');
hud.add([healthBar, healthText]);

// Move everything at once
hud.setPosition(50, 50);

// Scale and rotate propagate to children
hud.setScale(1.5);
hud.setRotation(0.1);

// Alpha affects all children
hud.setAlpha(0.8);

// Nested containers
const inventory = this.add.container(300, 500);
for (let i = 0; i < 5; i++) {
    const slot = this.add.container(i * 55, 0);
    slot.add([
        this.add.rectangle(0, 0, 48, 48, 0x333333),
        this.add.image(0, 0, `item-${i}`)
    ]);
    inventory.add(slot);    // Container inside Container
}

const bgLayer = this.add.layer();
const entityLayer = this.add.layer();
const uiLayer = this.add.layer();

// Add objects -- they render in layer order, then by depth within layer
bgLayer.add(this.add.image(400, 300, 'sky'));
entityLayer.add(player);
entityLayer.add(enemy);
uiLayer.add(scoreText);

// Control depth of layers themselves
bgLayer.setDepth(0);
entityLayer.setDepth(1);
uiLayer.setDepth(2);

// Children set depth within their layer
enemy.setDepth(5);   // relative to entityLayer, not the Scene

// Apply shared effects to entire layer
entityLayer.setAlpha(0.5);
entityLayer.setVisible(false);
entityLayer.setBlendMode(Phaser.BlendModes.ADD);

// createMultiple accepts a GroupCreateConfig or array of them
const coins = this.add.group();

coins.createMultiple({
    key: 'coin',
    quantity: 20,
    setXY: { x: 50, y: 100, stepX: 40, stepY: 0 },
    setScale: { x: 0.5, y: 0.5 },
    setRotation: { value: 0, step: 0.1 },   // each rotated 0.1 more than previous
    setAlpha: { value: 1 },
    setOrigin: { x: 0.5, y: 0.5 },
    setDepth: { value: 5 },
    gridAlign: {
        width: 5,
        height: 4,
        cellWidth: 48,
        cellHeight: 48,
        x: 100,
        y: 200
    }
});

// Multiple configs at once (creates two different sets)
coins.createMultiple([
    { key: 'gold-coin', quantity: 10, setXY: { x: 50, y: 100, stepX: 30 } },
    { key: 'silver-coin', quantity: 10, setXY: { x: 50, y: 200, stepX: 30 } }
]);

const enemies = this.add.group();

// Get all children as array
const all = enemies.getChildren();
const active = enemies.getMatching('active', true);

// Batch property operations
enemies.setXY(200, 300);
enemies.incX(5);                    // add 5 to each member's x
enemies.setVisible(false);
enemies.propertyValueSet('tintTopLeft', 0xff0000);
enemies.playAnimation('walk');

// Stepping: apply incremental values across members
enemies.setX(100, 50);             // first at x=100, next at 150, then 200...
enemies.setY(200, 30);             // first at y=200, next at 230, then 260...
enemies.setXY(100, 200, 50, 30);   // combined X and Y stepping
enemies.incXY(10, 5);              // add 10 to each x, 5 to each y
enemies.angle(0, 15);              // first at 0 deg, next at 15, then 30...
enemies.setAlpha(1, -0.1);         // first at 1.0, next at 0.9, then 0.8...
enemies.setScale(1, 0, 0.1, 0);   // scaleX: 1.0, 1.1, 1.2... (stepX=0.1)
enemies.setDepth(0, 1);            // depth 0, 1, 2, 3...
enemies.setOrigin(0.5);
enemies.setBlendMode(Phaser.BlendModes.ADD);
enemies.setTint(0xff0000);
enemies.shuffle();                  // randomize order in the group

Factory:  this.add.group(children?, config?)

Config types:
  GroupConfig       -- classType, name, active, maxSize, defaultKey, defaultFrame,
                       runChildUpdate, createCallback, removeCallback
  GroupCreateConfig -- key (required), classType, frame, quantity, visible, active,
                       repeat, yoyo, frameQuantity, max, setXY, setRotation,
                       setScale, setOrigin, setAlpha, setDepth, setScrollFactor,
                       hitArea, gridAlign

Key members:  children (Set), classType, maxSize, defaultKey, defaultFrame,
              active, runChildUpdate
Lifecycle:    create, createMultiple, add, addMultiple, remove, clear, destroy
Queries:      getFirst, getFirstAlive, getFirstDead, getLast, get, getChildren,
              getLength, getMatching, contains, countActive, getTotalUsed,
              getTotalFree, isFull
Pool:         get, getFirstDead, kill, killAndHide
Bulk ops:     setX/Y/XY, incX/Y/XY, setAlpha, setVisible, toggleVisible,
              playAnimation, propertyValueSet, propertyValueInc, setOrigin,
              setDepth, shuffle, setBlendMode, setTint

Factory:  this.add.container(x?, y?, children?)

Extends:  GameObject
Mixins:   AlphaSingle, BlendMode, ComputedSize, Depth, Mask, Transform, Visible

Key members:  list (Array), exclusive, maxSize, scrollFactorX/Y
Children:     add, addAt, remove, removeAt, removeBetween, removeAll
Queries:      getAt, getIndex, getByName, getFirst, getAll, getRandom, count
Ordering:     sort, swap, moveTo, moveUp, moveDown, sendToBack, bringToTop,
              moveAbove, moveBelow, reverse
Transform:    pointToContainer, getBounds, getBoundsTransformMatrix
Iteration:    each(cb, ctx), iterate(cb, ctx, ...args)
Config:       setExclusive, setScrollFactor(x, y, updateChildren)
Property:     length (read-only child count)

Factory:  this.add.layer(children?)

Extends:  Phaser.Structs.List
Mixins:   AlphaSingle, BlendMode, Depth, Filters, Mask, RenderSteps, Visible

Key members:  scene, displayList, sortChildrenFlag
Children:     add, remove (inherited from List)
Settings:     setAlpha, setBlendMode, setDepth, setVisible, setMask, setName,
              setActive, setState, setData, getData

No position, rotation, scale, scroll factor, input, or physics.
Cannot be added to a Container. Containers can be added to Layers.