/* =============================================
   Grammy Showcase — Ceramic Tile + Apple TV Parallax
   Glossy ceramic surface with specular light reflections.
   3D perspective tilt on hover. Spring-like animations.
   ============================================= */

:root {
  /* Colors */
  --color-bg: #f5f5f7;
  --color-text: #1d1d1f;
  --color-text-secondary: rgba(0, 0, 0, 0.45);
  --color-accent: #d4af37;
  --color-overlay: hsla(0, 0%, 97%, 0.92);

  /* Typography */
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Display",
    "Helvetica Neue", "Segoe UI", Roboto, Arial, sans-serif;
  --font-size-base: 20px;

  /* Spring easing computed from Apple's exact formulas (WWDC 2023 "Animate with Springs",
     corrected via Apple Developer Forums). Conversion: ζ = 1 - bounce, ωn = 2π / duration.
     Sampled via x(t) = 1 - e^(-ζωt)[cos(ωdt) + (ζ/√(1-ζ²))sin(ωdt)] at 21 points.

     --spring:        Apple .smooth — spring(duration: 0.3, bounce: 0) → ζ=1.0, ωn=20.94
     --spring-snappy: iOS 26 Liquid Glass — spring(duration: 0.35, bounce: 0.2) → ζ=0.8, ωn=17.95 */
  --spring: linear(0, 0.066, 0.206, 0.359, 0.500, 0.619, 0.715, 0.792, 0.848, 0.890, 0.922, 0.944, 0.960, 0.972, 0.981, 0.986, 0.991, 0.994, 0.996, 0.998, 1);
  --spring-snappy: linear(0, 0.079, 0.246, 0.437, 0.608, 0.747, 0.851, 0.923, 0.969, 0.995, 1.008, 1.012, 1.014, 1.013, 1.011, 1.008, 1.005, 1.003, 1.002, 1.001, 1);

  /* Durations */
  --duration: 600ms;
  --duration-fast: 350ms;

  /* Scale */
  --scale-up: 1.3;
  --scale-down: 0.93;

  /* Blur */
  --blur-radius: 12px;

  /* Perspective for 3D tilts */
  --perspective: 800px;
}

/* ---- Reset ---- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html, body {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  overflow: hidden;
  font-family: var(--font);
  font-size: var(--font-size-base);
  background: var(--color-bg);
  color: var(--color-text);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  -webkit-user-select: none;
  user-select: none;
  overscroll-behavior: none;
}

body::-webkit-scrollbar { display: none; }

/* ---- Header ---- */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 50;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0.3em;
  padding: 1.6em 2em 0.8em;
  pointer-events: none;
  transform: translateZ(0);
  transition: opacity var(--duration) var(--spring),
              filter var(--duration) var(--spring);
}

.header > * {
  pointer-events: auto;
}

.header__title {
  font-size: 1.4em;
  font-weight: 600;
  line-height: 1.2;
  white-space: nowrap;
  letter-spacing: -0.025em;
  color: var(--color-text);
  transition: opacity 200ms var(--spring), transform 200ms var(--spring);
}

.header__nav {
  font-weight: 200;
  margin-top: 2px;
  white-space: nowrap;
}

.header__nav-item {
  font-size: 1em;
  color: var(--color-text-secondary);
}

/* ---- Collection Switcher ---- */
.switcher__btn {
  font-family: var(--font);
  font-size: 0.85em;
  font-weight: 400;
  color: var(--color-text-secondary);
  background: none;
  border: none;
  padding: 0.2em 0.6em 0.4em;
  margin-left: 0.3em;
  cursor: pointer;
  transition: color 200ms;
}

.switcher__btn:first-child {
  margin-left: 0;
  padding-left: 0;
}

.switcher__btn:hover {
  color: var(--color-text);
}

.switcher__btn--active {
  color: var(--color-text);
  font-weight: 500;
}

.body--zoomed .header {
  opacity: 0;
  pointer-events: none;
}

/* ---- Overlay (frosted glass on zoom) ---- */
.overlay {
  position: fixed;
  inset: 0;
  background: var(--color-overlay);
  backdrop-filter: blur(20px) saturate(1.2);
  -webkit-backdrop-filter: blur(20px) saturate(1.2);
  opacity: 0;
  pointer-events: none;
  z-index: 4;
  transition: opacity var(--duration) var(--spring);
  will-change: opacity;
}

.body--zoomed .overlay {
  opacity: 1;
  pointer-events: auto;
}

/* ---- Gallery ---- */
.gallery {
  position: fixed;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: flex-start;
  z-index: 5;
  perspective: var(--perspective);
  overflow-x: auto;
  overflow-y: hidden;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
}

.gallery::-webkit-scrollbar {
  display: none;
}

.body--zoomed .gallery {
  pointer-events: none;
  overflow: hidden;
}

.body--stack-expanded .gallery {
  opacity: 0;
}

.gallery__track {
  display: flex;
  align-items: center;
  gap: 0;
  padding: 0 50vw; /* allows centering any card via native scroll */
  flex-shrink: 0;
}

/* ---- Gallery Card — Ceramic Tile ---- */
.card {
  position: relative;
  flex-shrink: 0;
  display: flex;
  align-items: flex-end;
  justify-content: center;
  cursor: pointer;
  transform-origin: center center;
  transform: perspective(var(--perspective)) rotateX(0deg) rotateY(0deg) scale3d(1, 1, 1);
  transform-style: preserve-3d;
  border-radius: 12px;
  overflow: hidden;
  background: #e8e8e8;

  /* Tactile multi-layer shadow: ambient + directional + inset bevel */
  box-shadow:
    0 1px 2px rgba(0, 0, 0, 0.08),
    0 4px 12px rgba(0, 0, 0, 0.06),
    0 12px 28px rgba(0, 0, 0, 0.08),
    inset 0 1px 0 rgba(255, 255, 255, 0.4),
    inset 0 -1px 0 rgba(0, 0, 0, 0.06);

  transition:
    transform var(--duration-fast) var(--spring),
    box-shadow var(--duration-fast) var(--spring),
    filter var(--duration) var(--spring),
    opacity var(--duration) var(--spring);
  will-change: transform, box-shadow, filter, opacity;
}

/* Ceramic gloss overlay — subtle specular highlight, never degrades artwork */
.card::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 2;
  border-radius: inherit;
  background: linear-gradient(
    135deg,
    rgba(255, 255, 255, 0.15) 0%,
    rgba(255, 255, 255, 0.04) 35%,
    rgba(255, 255, 255, 0) 50%,
    rgba(0, 0, 0, 0.01) 80%,
    rgba(0, 0, 0, 0.03) 100%
  );
  pointer-events: none;
  transition: opacity var(--duration-fast) var(--spring);
}

/* Dynamic light reflection — moves with mouse via JS, subtle */
.card::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 3;
  border-radius: inherit;
  background: radial-gradient(
    circle at var(--mouse-x, 50%) var(--mouse-y, 50%),
    rgba(255, 255, 255, 0.25) 0%,
    rgba(255, 255, 255, 0.06) 35%,
    rgba(255, 255, 255, 0) 55%
  );
  opacity: 0;
  pointer-events: none;
  transition: opacity 300ms ease;
}

/* Show dynamic light on hover */
.card:hover::after {
  opacity: 1;
}

/* Ceramic edge highlight — beveled edges on all four sides */
.card__edge-highlight {
  position: absolute;
  inset: 0;
  z-index: 4;
  border-radius: inherit;
  pointer-events: none;
  /* Top: bright catch light. Left: subtle. Right/bottom: dark for depth */
  border-top: 1px solid rgba(255, 255, 255, 0.55);
  border-left: 1px solid rgba(255, 255, 255, 0.2);
  border-right: 1px solid rgba(0, 0, 0, 0.04);
  border-bottom: 1px solid rgba(0, 0, 0, 0.08);
  opacity: 1;
}

/* Hover state — lifted off surface with deeper shadow */
.card.card--hovering {
  box-shadow:
    0 2px 4px rgba(0, 0, 0, 0.06),
    0 8px 20px rgba(0, 0, 0, 0.08),
    0 24px 48px rgba(0, 0, 0, 0.12),
    0 48px 80px rgba(0, 0, 0, 0.06),
    inset 0 1px 0 rgba(255, 255, 255, 0.5),
    inset 0 -1px 0 rgba(0, 0, 0, 0.04);
}

/* Non-active cards when zoomed */
.body--zoomed .card {
  transform: perspective(var(--perspective)) scale3d(var(--scale-down), var(--scale-down), 1);
  filter: blur(var(--blur-radius));
  opacity: 0;
  pointer-events: none;
}

/* Remove gloss on non-active zoomed cards */
.body--zoomed .card::before,
.body--zoomed .card::after {
  opacity: 0;
}

/* Active/zoomed card */
.body--zoomed .card.card--active {
  transform: perspective(var(--perspective)) scale3d(var(--scale-up), var(--scale-up), 1);
  filter: blur(0px);
  opacity: 1;
  pointer-events: auto;
  z-index: 20;
  cursor: default;
  box-shadow:
    0 4px 8px rgba(0, 0, 0, 0.06),
    0 16px 32px rgba(0, 0, 0, 0.1),
    0 40px 80px rgba(0, 0, 0, 0.14),
    inset 0 1px 0 rgba(255, 255, 255, 0.35),
    inset 0 -1px 0 rgba(0, 0, 0, 0.05);
}

/* Keep gloss on active card */
.body--zoomed .card.card--active::before {
  opacity: 1;
}

.card__image {
  width: 100%;
  height: 100%;
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center center;
  transform: translateZ(0);
}

/* Loading state */
.card__loader {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: opacity 200ms;
  z-index: 1;
}

.card__loader.visible {
  opacity: 1;
}

.card__loader-spinner {
  width: 24px;
  height: 24px;
  border: 2px solid rgba(0, 0, 0, 0.08);
  border-top-color: var(--color-accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ---- Detail Panel ---- */
.detail {
  position: fixed;
  z-index: 25;
  pointer-events: none;
  transform: translateZ(0);
  opacity: 0;
  transition: opacity var(--duration) var(--spring),
              transform var(--duration) var(--spring);
}

.body--zoomed .detail {
  opacity: 1;
  pointer-events: auto;
}

/* Hide detail panel during stack-expanded (only show when a song is selected) */
.body--stack-expanded .detail {
  opacity: 0 !important;
  pointer-events: none !important;
}

.body--stack-song-selected .detail {
  opacity: 1 !important;
  pointer-events: auto !important;
}

.detail__content {
  display: flex;
  flex-direction: column;
  transform: translateZ(0);
}

/* Staggered text reveal: children start invisible when animation is armed,
   then fade+slide in with staggered delays when .detail--revealing is added.
   Scoped to .detail--armed so children are visible by default (no flash). */
.detail--armed .detail__content > :not(.detail__meta),
.detail--armed .detail__meta > * {
  opacity: 0;
  transform: translateY(8px);
  transition: opacity 300ms var(--spring), transform 300ms var(--spring);
  transition-delay: calc(var(--reveal-i, 0) * 40ms);
}
.detail--revealing .detail__content > :not(.detail__meta),
.detail--revealing .detail__meta > * {
  opacity: 1;
  transform: translateY(0);
}
/* Instant reset when hiding (no reverse stagger) */
.detail--hiding .detail__content > :not(.detail__meta),
.detail--hiding .detail__meta > * {
  transition-delay: 0ms;
}

.detail__meta {
  display: flex;
  flex-direction: column;
  margin-bottom: 0.4em;
}

.detail__category {
  font-size: 0.65em;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-accent);
  font-weight: 600;
  margin-bottom: 0.15em;
}

.detail__year {
  font-size: 0.75em;
  color: var(--color-text-secondary);
  font-weight: 400;
  margin-bottom: 0;
}

.detail__song {
  font-size: 1.5em;
  font-weight: 700;
  margin-bottom: 0.1em;
  letter-spacing: -0.02em;
  line-height: 1.2;
}

.detail__artist {
  font-size: 1em;
  font-weight: 400;
  color: var(--color-text);
  margin-bottom: 0.05em;
}

.detail__album {
  font-size: 0.8em;
  font-weight: 400;
  color: var(--color-text-secondary);
  margin-bottom: 0;
}

/* ---- Transport Controls ---- */
.detail__transport {
  display: flex;
  align-items: center;
  gap: 1em;
  margin-top: 0.8em;
}

.detail__skip-btn {
  width: 1.4em;
  height: 1.4em;
  border: none;
  background: none;
  cursor: pointer;
  padding: 0;
  color: var(--color-text);
  opacity: 0.45;
  transition: opacity 200ms, color 200ms;
}

.detail__skip-btn:hover {
  opacity: 1;
  color: var(--color-accent);
}

.detail__skip-btn svg {
  width: 100%;
  height: 100%;
}

/* ---- Play Button ---- */
.detail__play-btn {
  position: relative;
  width: 2.6em;
  height: 2.6em;
  border: none;
  background: none;
  cursor: pointer;
  padding: 0;
  color: var(--color-text);
  transition: color 200ms;
}

.detail__play-btn:hover {
  color: var(--color-accent);
}

.detail__play-icon {
  width: 100%;
  height: 100%;
  overflow: visible;
}

.detail__progress {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  transform: rotate(-90deg);
  opacity: 0;
  transition: opacity 200ms;
}

.detail__progress.visible {
  opacity: 1;
}

.detail__progress-ring {
  fill: none;
  stroke: var(--color-accent);
  stroke-width: 3.5;
  stroke-dasharray: 206.15;
  stroke-dashoffset: 206.15;
  stroke-linecap: round;
}

/* ---- Back Button ---- */
.back-btn {
  position: fixed;
  top: 2em;
  left: 2em;
  z-index: 60;
  width: 2em;
  height: 2em;
  border: none;
  background: none;
  cursor: pointer;
  color: var(--color-text);
  opacity: 0.3;
  transition: opacity 200ms;
  padding: 0;
}

.back-btn:hover {
  opacity: 1;
}

.back-btn svg {
  width: 100%;
  height: 100%;
}

/* ---- Responsive ---- */
/* ---- Tablet ---- */
@media (max-width: 768px) {
  :root {
    --font-size-base: 16px;
    --scale-up: 1.0;
    --scale-down: 0.95;
  }

  .header {
    padding: 1.2em 1.2em 0;
    gap: 0.3em;
  }

  .header__title {
    font-size: 1.3em;
    margin-bottom: 0;
  }

  /* Horizontal scrollable tab bar for playlist switcher */
  .header__nav {
    display: flex;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    margin: 0 -1.2em;
    padding: 0 1.2em;
    gap: 0;
  }
  .header__nav::-webkit-scrollbar { display: none; }

  .switcher__btn {
    font-size: 0.75em;
    white-space: nowrap;
    flex-shrink: 0;
    padding: 0.3em 0.5em 0.5em;
  }

  .back-btn {
    top: 1.2em;
    left: 1.2em;
    width: 36px;
    height: 36px;
  }

  .card { border-radius: 10px; }
}

/* ---- Phone ---- */
@media (max-width: 480px) {
  :root { --font-size-base: 14px; }

  .header {
    padding: 0.8em 0.8em 0;
  }

  .header__title { font-size: 1.15em; }

  .header__nav {
    margin: 0 -0.8em;
    padding: 0 0.8em;
  }

  .switcher__btn { font-size: 0.7em; }

  .back-btn {
    top: 0.8em;
    left: 0.8em;
    width: 32px;
    height: 32px;
  }

  .card { border-radius: 8px; }

  /* Allow song titles to wrap on small screens */
  .detail__song {
    font-size: 1.2em;
    white-space: normal;
    word-wrap: break-word;
  }

  .detail__artist { font-size: 0.9em; }
  .detail__album { font-size: 0.75em; }
  .detail__category { font-size: 0.5em; }

  .detail__transport {
    gap: 0.8em;
    margin-top: 0.5em;
  }
  .detail__play-btn { width: 2.2em; height: 2.2em; }
  .detail__skip-btn { width: 1.2em; height: 1.2em; }
}

/* =============================================
   Stacked Collection Layout
   ============================================= */

/* ---- Stack Card (gallery view) ---- */
.stack-card {
  position: relative;
  flex-shrink: 0;
  width: 340px;
  height: 340px;
  cursor: pointer;
  transform-origin: center center;
  transform: perspective(var(--perspective)) rotateX(0deg) rotateY(0deg) scale3d(1, 1, 1);
  transform-style: preserve-3d;
  transition:
    transform var(--duration-fast) var(--spring),
    box-shadow var(--duration-fast) var(--spring),
    filter var(--duration) var(--spring),
    opacity var(--duration) var(--spring);
  will-change: transform, box-shadow, filter, opacity;
}

.stack-card__layer {
  position: absolute;
  width: 100%;
  height: 100%;
  border-radius: 12px;
  overflow: hidden;
  background: #e8e8e8;
  background-size: cover;
  background-position: center;
  box-shadow:
    0 1px 2px rgba(0, 0, 0, 0.08),
    0 4px 12px rgba(0, 0, 0, 0.06),
    0 12px 28px rgba(0, 0, 0, 0.08),
    inset 0 1px 0 rgba(255, 255, 255, 0.4),
    inset 0 -1px 0 rgba(0, 0, 0, 0.06);
  transition: transform 500ms var(--spring), opacity 500ms var(--spring);
}

/* Bottom layer: rotated, offset */
.stack-card__layer:nth-child(1) {
  transform: translate(-8px, 6px) rotate(-3deg);
  z-index: 1;
}

/* Middle layer */
.stack-card__layer:nth-child(2) {
  transform: translate(4px, -4px) rotate(1.5deg);
  z-index: 2;
}

/* Top layer: centered, dominant */
.stack-card__layer:nth-child(3) {
  transform: translate(0, 0) rotate(0deg);
  z-index: 3;
}

.stack-card__label {
  position: absolute;
  bottom: -28px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 10;
  font-size: 0.7em;
  font-weight: 500;
  color: var(--color-text-secondary);
  white-space: nowrap;
  letter-spacing: 0.02em;
}

.stack-card.stack-card--hovering {
  box-shadow:
    0 2px 4px rgba(0, 0, 0, 0.06),
    0 8px 20px rgba(0, 0, 0, 0.08),
    0 24px 48px rgba(0, 0, 0, 0.12),
    0 48px 80px rgba(0, 0, 0, 0.06);
}

.body--zoomed .stack-card {
  filter: blur(var(--blur-radius));
  opacity: 0;
  pointer-events: none;
}

/* ---- Stack Expanded View ---- */
.stack-view {
  position: fixed;
  inset: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: center;
  pointer-events: none;
  opacity: 0;
  overflow: visible;
  transition: opacity 400ms var(--spring);
  /* Solid background — no backdrop-filter (it creates a clipping paint layer that
     cuts off FLIP-animated cards and causes scroll flicker) */
  background: var(--color-bg);
}

.stack-view--visible {
  opacity: 1;
  pointer-events: auto;
}

.stack-view__scroller {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 24px;
  padding: 40px 0;
  max-height: 100vh;
  overflow-y: auto;
  overflow-x: hidden;
  scrollbar-width: none;
  -webkit-overflow-scrolling: touch;
  width: 300px;
  position: absolute;
  left: 15%;
}

/* During expand/collapse animation, disable clipping so FLIP cards aren't cut off */
/* NOTE: Only overflow changes — max-height stays at 100vh to keep card positions consistent */
.stack-view__scroller--animating {
  overflow: visible !important;
}

.stack-view__scroller::-webkit-scrollbar {
  display: none;
}

/* Cards inside expanded stack view — simplified rendering for smooth scroll.
   Hide pseudo-elements (gloss/reflection) and reduce box-shadow to minimize paint cost. */
.stack-view .card {
  width: 220px !important;
  height: 220px !important;
  margin-left: 0 !important;
  flex-shrink: 0;
  opacity: 0;
  transform: translateY(40px) scale(0.95);
  will-change: auto;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.12), inset 0 1px 0 rgba(255, 255, 255, 0.3);
}

/* Hide decorative pseudo-elements in stack view — eliminates paint flicker during scroll */
.stack-view .card::before,
.stack-view .card::after {
  display: none !important;
}

.stack-view .card.stack-view__card--visible {
  opacity: 1;
  transform: none;
}

/* After expand animation, promote cards to GPU layers for smooth scroll */
.stack-view__scroller--scrollable .card {
  will-change: transform !important;
}

.stack-view .card.stack-view__card--selected {
  transform: scale(1.02);
  box-shadow:
    0 4px 8px rgba(0, 0, 0, 0.06),
    0 16px 32px rgba(0, 0, 0, 0.1),
    0 40px 80px rgba(0, 0, 0, 0.14),
    inset 0 1px 0 rgba(255, 255, 255, 0.35),
    inset 0 -1px 0 rgba(0, 0, 0, 0.05);
  z-index: 20;
}

/* Override body--zoomed hiding rule for cards inside stack-view */
.body--stack-expanded .stack-view .card {
  transform: translateY(40px) scale(0.95) !important;
  filter: none !important;
  opacity: 0;
  pointer-events: auto;
  will-change: auto;
  /* --spring-snappy defined at line 24 — subtle overshoot for spatial transforms */
  transition: transform 450ms var(--spring-snappy),
              opacity 350ms var(--spring),
              box-shadow 350ms var(--spring),
              filter 350ms var(--spring);
}

.body--stack-expanded .stack-view .card.stack-view__card--visible {
  opacity: 1 !important;
  transform: none !important;
}

/* Dim non-selected cards when a song is selected */
.body--stack-song-selected .stack-view .card:not(.stack-view__card--selected) {
  opacity: 0.4;
  filter: blur(4px);
  pointer-events: auto;
  transition: opacity 300ms var(--spring), filter 300ms var(--spring);
}

/* (reserved for future use) */

/* ---- Stack Responsive ---- */
@media (max-width: 768px) {
  .stack-card {
    width: 260px;
    height: 260px;
  }

  .stack-view__scroller {
    width: 240px;
    left: 10%;
  }

  .stack-view .card {
    width: 180px !important;
    height: 180px !important;
  }
}

@media (max-width: 480px) {
  .stack-card {
    width: 200px;
    height: 200px;
  }

  .stack-view__scroller {
    width: 200px;
    left: 5%;
  }

  .stack-view .card {
    width: 150px !important;
    height: 150px !important;
  }
}