@font-face {
  font-family: "Liebe Heide";
  src: url("fonts/LiebeHeide.otf") format("opentype");
  font-weight: normal;
  font-style: normal;
  font-display: swap;
}

:root {
  --bg: black;
  --card-bg: #fffdfa;
  --fg: #2b2b2b;
  --muted: #9a9a9a;
  --accent: #a6624a;
  --border: #e8e2da;
  --max-width: 550px;
}

* {
  box-sizing: border-box;
}

html, body {
  height: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

.stage {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  overflow: hidden;
}

.card-scene {
  position: relative;
  z-index: 1;
  perspective: 2000px;
  width: 100%;
  max-width: var(--max-width);
  display: flex;
  justify-content: center;
  transform: translateX(0);
  transition: transform 0.9s cubic-bezier(0.65, 0, 0.35, 1);
}

.card-scene.open {
  transform: translateX(50%);
}

.card {
  position: relative;
  width: 100%;
  transform-style: preserve-3d;
  transform: rotateX(0deg) rotateY(0deg);
  transition: transform 0.15s ease-out;
  will-change: transform;
}

.card-inside {
  position: relative;
  padding: 3rem 3rem;
  text-align: left;
  background: var(--card-bg);
  border: 1px solid var(--border);
  box-shadow:
    0 40px 80px -30px rgba(0, 0, 0, 0.22),
    0 12px 24px -12px rgba(0, 0, 0, 0.12);
}

.card.open .card-inside {
  cursor: pointer;
}

.card-cover {
  appearance: none;
  position: absolute;
  inset: 0;
  margin: 0;
  padding: 0;
  border: none;
  background: none;
  color: inherit;
  cursor: pointer;
  transform-style: preserve-3d;
  transform-origin: left center;
  transform: rotateY(0deg);
  transition: transform 0.9s cubic-bezier(0.65, 0, 0.35, 1);
}

.card.open .card-cover {
  transform: rotateY(-155deg);
  pointer-events: none;
}

.cover-face {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 2rem;
  overflow: hidden;
  font-family: inherit;
  color: var(--fg);
  background: var(--card-bg);
  border: 1px solid var(--border);
  box-shadow:
    0 40px 80px -30px rgba(0, 0, 0, 0.22),
    0 12px 24px -12px rgba(0, 0, 0, 0.12);
  backface-visibility: hidden;
}

.cover-back {
  transform: rotateY(180deg);
}

.cover-title {
  display: contents;
  font-family: "Rock 3D", cursive;
  text-transform: uppercase;
}

.cover-letters {
  position: absolute;
  inset: 6% 4% 16% 4%;
  font-size: 1.9rem;
}

.cover-letter {
  position: absolute;
  transform: translate(-50%, -50%) rotate(var(--rot, 0deg)) scale(var(--scale, 1));
}

.cover-hint {
  position: absolute;
  left: 50%;
  bottom: 6%;
  transform: translateX(-50%);
  margin: 0;
  font-size: 0.8rem;
  color: var(--muted);
}

.letter p {
  margin: 0 0 1.2rem;
  font-family: "Liebe Heide", "Segoe Script", cursive;
  font-weight: normal;
  font-size: 1.3rem;
  line-height: 1.6;
  color: var(--fg);
}

.letter p:last-child {
  margin-bottom: 0;
}

.emphasis {
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 1px;
  text-decoration-skip-ink: none;
  color: mediumslateblue;
}

.letter .closing {
  text-align: right;
  font-size: 1.55rem;
  color: var(--accent);
}

.signature {
  display: block;
  width: 55px;
  height: auto;
  margin: -20px 0 0 auto;
  mix-blend-mode: multiply;
  opacity: 0.7;
}

.collage {
  position: absolute;
  inset: 0;
  z-index: 0;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.collage-scrim {
  position: absolute;
  inset: 0;
  z-index: 0;
  background: rgba(0, 0, 0, 0.5);
  pointer-events: none;
}

.collage-row {
  flex: 1;
  min-height: 0;
  overflow: hidden;
}

.collage-track {
  display: flex;
  height: 100%;
  width: max-content;
  animation: collage-scroll 80s linear infinite;
}

.collage-track img {
  display: block;
  height: 100%;
  width: auto;
  flex-shrink: 0;
  object-fit: cover;
}

@keyframes collage-scroll {
  from {
    transform: translateX(0);
  }
  to {
    transform: translateX(-50%);
  }
}

.stars {
  position: absolute;
  inset: 0;
  z-index: 1;
  overflow: hidden;
  pointer-events: none;
}

.star {
  position: absolute;
  background: #fff;
  clip-path: polygon(
    50% 0%, 63% 37%, 100% 50%, 63% 63%,
    50% 100%, 37% 63%, 0% 50%, 37% 37%
  );
  opacity: 0;
  animation: twinkle 4s ease-in-out infinite;
}

@keyframes twinkle {
  0%, 100% {
    opacity: 0;
    transform: scale(0.3);
  }
  50% {
    opacity: 1;
    transform: scale(1);
  }
}

@media (max-width: 640px) {
  .card-inside,
  .cover-face {
    padding: 2.25rem 1.75rem;
  }
  .letter p {
    font-size: 1.1rem;
  }
  .letter .closing {
    font-size: 1.3rem;
  }
  .cover-letters {
    font-size: 1.4rem;
    inset: 8% 3% 18% 3%;
  }
  .card-scene.open {
    transform: translateX(0);
  }
}

@media (prefers-reduced-motion: reduce) {
  .card,
  .card-cover,
  .card-scene {
    transition: none;
  }
  .collage-track {
    animation: none;
  }
  .star {
    animation: none;
  }
}