MaterialTheme(motionScheme = MotionScheme.expressive()) {
    // children read tokens via MaterialTheme.motionScheme.*
}

@Composable
fun ExpressiveHero() {
    var expanded by remember { mutableStateOf(false) }
    MaterialTheme(motionScheme = MotionScheme.expressive()) {
        val transition = updateTransition(targetState = expanded, label = "expand")
        val height by transition.animateDp(
            transitionSpec = { MaterialTheme.motionScheme.slowSpatialSpec() },
            label = "height"
        ) { if (it) 400.dp else 100.dp }
        val alpha by transition.animateFloat(
            transitionSpec = { MaterialTheme.motionScheme.defaultEffectsSpec() },
            label = "alpha"
        ) { if (it) 1f else 0f }

        Card(
            modifier = Modifier
                .fillMaxWidth()
                .height(height)
                .clickable { expanded = !expanded }
        ) {
            Box(modifier = Modifier.alpha(alpha)) {
                Text("Detail content", modifier = Modifier.padding(24.dp))
            }
        }
    }
}

val morph = remember { Morph(MaterialShapes.Circle, MaterialShapes.Cookie4Sided) }
val progress by animateFloatAsState(
    targetValue = if (active) 1f else 0f,
    animationSpec = MaterialTheme.motionScheme.slowSpatialSpec(),
    label = "morph"
)
Box(
    modifier = Modifier
        .size(96.dp)
        .clip(GenericShape { size, _ ->
            addPath(
                morph.toPath(progress).asAndroidPath().asComposePath()
            )
        })
        .background(MaterialTheme.colorScheme.primary)
)

@Composable
fun ShaderEffect(content: @Composable () -> Unit) {
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU) {
        // Android 12 and below: skip the shader, render content as-is.
        content()
        return
    }
    val shader = remember { RuntimeShader(AGSL_SOURCE) }
    val time by produceState(0f) {
        while (true) {
            withFrameMillis { ms ->
                value = ms / 1000f
            }
        }
    }
    Box(
        modifier = Modifier
            .onSizeChanged {
                shader.setFloatUniform("resolution", it.width.toFloat(), it.height.toFloat())
            }
            .graphicsLayer {
                shader.setFloatUniform("time", time)
                renderEffect = RenderEffect
                    .createRuntimeShaderEffect(shader, "image")
                    .asComposeRenderEffect()
            }
    ) { content() }
}

// ripple.agsl
uniform float2 resolution;
uniform float2 origin;
uniform float time;
uniform shader image;

half4 main(float2 fragCoord) {
    float2 toOrigin = fragCoord - origin;
    float dist = length(toOrigin);
    float wave = sin(dist * 0.05 - time * 8.0) * 0.05;
    float falloff = 1.0 / max(dist * 0.01, 1.0);
    float2 dir = toOrigin / max(dist, 0.0001);
    float2 displaced = fragCoord + dir * wave * falloff * 50.0;
    return image.eval(displaced);
}

@Composable
fun RippleSurface(content: @Composable BoxScope.() -> Unit) {
    if (Build.VERSION.SDK_INT < 33) { Box { content() }; return }
    val shader = remember { RuntimeShader(RIPPLE_AGSL) }
    var origin by remember { mutableStateOf(Offset.Zero) }
    var startMs by remember { mutableStateOf<Long?>(null) }
    val time by produceState(0f, startMs) {
        if (startMs == null) { value = 0f; return@produceState }
        val begin = startMs!!
        while (true) {
            withFrameMillis { now ->
                value = (now - begin) / 1000f
            }
        }
    }
    Box(
        modifier = Modifier
            .onSizeChanged {
                shader.setFloatUniform("resolution", it.width.toFloat(), it.height.toFloat())
            }
            .pointerInput(Unit) {
                detectTapGestures { tap ->
                    origin = tap
                    startMs = System.currentTimeMillis()
                }
            }
            .graphicsLayer {
                shader.setFloatUniform("origin", origin.x, origin.y)
                shader.setFloatUniform("time", time)
                renderEffect = RenderEffect
                    .createRuntimeShaderEffect(shader, "image")
                    .asComposeRenderEffect()
            },
        content = content
    )
}

uniform float time;
uniform shader image;

half4 main(float2 fragCoord) {
    half4 color = image.eval(fragCoord);
    float n = fragCoord.x * 0.01 + fragCoord.y * 0.005 + time * 0.3;
    half3 rainbow = half3(
        sin(n * 2.0) * 0.5 + 0.5,
        sin(n * 2.0 + 2.094) * 0.5 + 0.5,
        sin(n * 2.0 + 4.188) * 0.5 + 0.5
    );
    half luma = dot(color.rgb, half3(0.299, 0.587, 0.114));
    return half4(mix(color.rgb, rainbow * luma * 2.0, 0.5), color.a);
}

uniform float2 resolution;
uniform shader image;

half4 main(float2 fragCoord) {
    float2 uv = fragCoord / resolution;
    // Chromatic aberration: sample R, G, B at slightly different offsets
    float2 ca = (uv - 0.5) * 0.004;
    half r = image.eval(fragCoord + ca * resolution).r;
    half g = image.eval(fragCoord).g;
    half b = image.eval(fragCoord - ca * resolution).b;
    half4 base = half4(r, g, b, 1.0);
    // Soft edge tint: brighten near borders for that frosted look
    float edge = smoothstep(0.45, 0.5, max(abs(uv.x - 0.5), abs(uv.y - 0.5)));
    half3 tinted = base.rgb + half3(edge * 0.08);
    return half4(tinted, 0.85);
}

Canvas(modifier = Modifier.size(200.dp)) {
    // 'this' is DrawScope - size, drawCircle, drawPath, drawRect...
    drawCircle(Color.Blue, radius = size.minDimension / 2)
    drawPath(myPath, color = Color.White, style = Stroke(width = 4.dp.toPx()))
}

@Composable
fun AnimatedWave() {
    val infinite = rememberInfiniteTransition(label = "wave")
    val phase by infinite.animateFloat(
        initialValue = 0f,
        targetValue = 2 * PI.toFloat(),
        animationSpec = infiniteRepeatable(
            animation = tween(3000, easing = LinearEasing)
        ),
        label = "phase"
    )
    Canvas(modifier = Modifier.fillMaxWidth().height(80.dp)) {
        val path = Path()
        var x = 0
        while (x <= size.width.toInt()) {
            val y = size.height / 2 + sin(x * 0.05f + phase) * 20f
            if (x == 0) path.moveTo(x.toFloat(), y) else path.lineTo(x.toFloat(), y)
            x += 2
        }
        drawPath(path, color = Color.Blue, style = Stroke(width = 2.dp.toPx()))
    }
}

data class Particle(var x: Float, var y: Float, var vx: Float, var vy: Float, var life: Float)

@Composable
fun ParticleField() {
    val particles = remember {
        mutableStateListOf<Particle>().apply {
            repeat(50) {
                add(Particle(
                    x = Random.nextFloat() * 1000f,
                    y = Random.nextFloat() * 1000f,
                    vx = (Random.nextFloat() - 0.5f) * 4f,
                    vy = (Random.nextFloat() - 0.5f) * 4f,
                    life = 1f
                ))
            }
        }
    }
    LaunchedEffect(Unit) {
        while (true) {
            withFrameMillis { /* tick */ }
            particles.forEachIndexed { i, p ->
                p.x += p.vx
                p.y += p.vy
                p.life -= 0.01f
                if (p.life <= 0f) {
                    p.x = Random.nextFloat() * 1000f
                    p.y = Random.nextFloat() * 1000f
                    p.life = 1f
                }
            }
        }
    }
    Canvas(modifier = Modifier.fillMaxSize()) {
        particles.forEach { p ->
            drawCircle(
                color = Color.White.copy(alpha = p.life),
                radius = 2.dp.toPx(),
                center = Offset(p.x, p.y)
            )
        }
    }
}

// BAD - every interaction overshoots, UI feels like a bouncy castle
MaterialTheme(motionScheme = MotionScheme.expressive()) {
    AppRoot()
}

// GOOD - Standard for chrome, scope Expressive to hero moments
MaterialTheme(motionScheme = MotionScheme.standard()) {
    NavigationScaffold {
        // Hero detail screen overrides locally
        MaterialTheme(motionScheme = MotionScheme.expressive()) {
            HeroDetail()
        }
    }
}

// BAD - crashes on Android 12 and below
val shader = remember { RuntimeShader(AGSL_SOURCE) }

// GOOD - gate on SDK level, provide fallback
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
    ShaderEffect { content() }
} else {
    Box(modifier = Modifier.background(fallbackGradient)) { content() }
}

// BAD - any state change in the parent triggers a recompose of the Canvas
Canvas(modifier = Modifier.fillMaxSize()) {
    drawCircle(color = if (viewModel.isActive) Color.Red else Color.Blue, radius = 50f)
}

// GOOD - hoist the reads, derive a stable value
val color by remember { derivedStateOf { if (viewModel.isActive) Color.Red else Color.Blue } }
Canvas(modifier = Modifier.fillMaxSize()) {
    drawCircle(color = color, radius = 50f)
}

// BAD - 4 render passes per frame, GPU melts on mid-range devices
.graphicsLayer { renderEffect = blurEffect }
.graphicsLayer { renderEffect = chromaticEffect }
.graphicsLayer { renderEffect = noiseEffect }
.graphicsLayer { renderEffect = vignetteEffect }

// GOOD - one shader doing all the math in a single pass
.graphicsLayer { renderEffect = combinedGlassEffect }

// BAD - new Path every frame, GC stutter
Canvas(modifier = Modifier.fillMaxSize()) {
    val path = Path()
    points.forEach { path.lineTo(it.x, it.y) }
    drawPath(path, color = Color.Black)
}

// GOOD - reuse a remembered Path, rewind each frame
val path = remember { Path() }
Canvas(modifier = Modifier.fillMaxSize()) {
    path.rewind()
    points.forEach { path.lineTo(it.x, it.y) }
    drawPath(path, color = Color.Black)
}