Spotify：カラー、エモーション、そしてスケールするデザイン

Album Art → Dominant Color Extraction → Vibrancy Filter → Contrast Check → Gradient Generation

/* Spotify's dynamic gradient approach */
.album-header {
  background: linear-gradient(
    to bottom,
    var(--extracted-color) 0%,
    rgba(18, 18, 18, 1) 100%
  );
  min-height: 340px;
  padding: 24px;
  transition: background 300ms ease;
}

/* The extracted color becomes a CSS custom property */
:root {
  --extracted-color: #1a6b3c;  /* Set dynamically per album */
  --extracted-color-light: #2d9d5a;
  --surface-base: #121212;
  --surface-elevated: #1a1a1a;
  --text-primary: #ffffff;
  --text-secondary: #b3b3b3;
}

:root {
  /* Surface hierarchy */
  --background-base: #121212;
  --background-elevated: #1a1a1a;
  --background-tinted: #282828;
  --background-highlight: #333333;

  /* Text hierarchy */
  --text-base: #ffffff;
  --text-subdued: #a7a7a7;
  --text-disabled: #6a6a6a;

  /* Brand accent */
  --essential-positive: #1ed760;  /* The green */
  --essential-negative: #e91429;
  --essential-announcement: #3d91f4;

  /* Elevation through brightness, not shadow */
  --card-surface: #181818;
  --card-surface-hover: #282828;
}

/* Cards get lighter on hover — inverse of light-mode convention */
.card {
  background: var(--card-surface);
  border-radius: 8px;
  padding: 16px;
  transition: background-color 200ms ease;
}

.card:hover {
  background: var(--card-surface-hover);
}

/* Spotify's typographic hierarchy */
.type-canon {
  font-size: 96px;
  font-weight: 900;
  line-height: 1.0;
  letter-spacing: -0.04em;
  /* Used in Wrapped, marketing, hero moments */
}

.type-title-large {
  font-size: 32px;
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.02em;
  /* Album titles, playlist names */
}

.type-title-medium {
  font-size: 24px;
  font-weight: 700;
  line-height: 1.2;
  /* Section headers on Home */
}

.type-title-small {
  font-size: 16px;
  font-weight: 700;
  line-height: 1.3;
  /* Card titles */
}

.type-body {
  font-size: 14px;
  font-weight: 400;
  line-height: 1.5;
  color: var(--text-subdued);
  /* Descriptions, metadata */
}

.type-caption {
  font-size: 11px;
  font-weight: 400;
  line-height: 1.4;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  color: var(--text-subdued);
  /* Labels, overlines */
}

HOME FEED LAYOUT:
┌─────────────────────────────────────────────────────────┐
│  Good evening                                           │
│  ┌──────────┬──────────┬──────────┐                     │
│  │ ■ Daily  │ ■ Liked  │ ■ Chill  │  ← Quick-access    │
│  │   Mix 1  │   Songs  │   Hits   │    (2-column grid)  │
│  ├──────────┼──────────┼──────────┤                     │
│  │ ■ Rock   │ ■ Jazz   │ ■ Focus  │                     │
│  │   Clas.  │   Vibes  │   Flow   │                     │
│  └──────────┴──────────┴──────────┘                     │
│                                                         │
│  Made for you                           [Show all →]    │
│  ┌────────┐ ┌────────┐ ┌────────┐ ┌────────┐           │
│  │        │ │        │ │        │ │        │           │
│  │  ■ Art │ │  ■ Art │ │  ■ Art │ │  ■ Art │  ← Scroll│
│  │        │ │        │ │        │ │        │           │
│  │ Discov │ │ Daily  │ │ Releas │ │ Repeat │           │
│  │ Weekly │ │ Mix 2  │ │ Radar  │ │ Rewind │           │
│  └────────┘ └────────┘ └────────┘ └────────┘           │
│                                                         │
│  Recently played                        [Show all →]    │
│  ┌────────┐ ┌────────┐ ┌────────┐ ┌────────┐           │
│  │ ○ Art  │ │  ■ Art │ │ ○ Art  │ │  ■ Art │           │
│  │ Artist │ │ Album  │ │ Artist │ │ Plist  │           │
│  └────────┘ └────────┘ └────────┘ └────────┘           │
└─────────────────────────────────────────────────────────┘

○ = circular (artist)   ■ = square with radius (album/playlist)

.content-card {
  width: 100%;
  background: var(--card-surface);
  border-radius: 8px;
  padding: 16px;
  cursor: pointer;
  transition: background-color 200ms ease;
  position: relative;
}

.content-card:hover {
  background: var(--card-surface-hover);
}

/* Play button appears on hover */
.content-card:hover .play-button {
  opacity: 1;
  transform: translateY(0);
}

.play-button {
  position: absolute;
  bottom: 88px;
  right: 16px;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--essential-positive);
  opacity: 0;
  transform: translateY(8px);
  transition: opacity 200ms ease, transform 200ms ease;
  box-shadow: 0 8px 16px rgba(0, 0, 0, 0.3);
}

.card-image {
  width: 100%;
  aspect-ratio: 1;
  border-radius: 4px;
  object-fit: cover;
  margin-bottom: 16px;
}

/* Artists get circular images */
.card-image--artist {
  border-radius: 50%;
}

WRAPPED STORY FORMAT:
┌─────────────────────────────────┐
│                                 │
│     Your top genre              │  ← Overline (caption)
│                                 │
│     INDIE                       │  ← Hero text (canon size)
│     ROCK                        │
│                                 │
│     You listened to 847         │  ← Supporting stat
│     indie rock songs            │
│     this year                   │
│                                 │
│     That's more than 94%        │  ← Social proof
│     of listeners                │
│                                 │
│  ┌───────────────────────────┐  │
│  │     Share to Instagram    │  │  ← CTA
│  └───────────────────────────┘  │
│                                 │
│           ● ○ ○ ○ ○             │  ← Story progress
└─────────────────────────────────┘
  Background: bold duotone gradient
  Typography: oversized, heavy weight
  Layout: centered, mobile-first