:root {
  /* Light Mode - Warm Earth Tones */
  --bg-color: #F5F0EB;
  --surface-color: #FEFCF9;
  --text-main: #2D2926;
  --text-muted: #8A847D;
  --primary: #C4A882;

  /* POS Colors Light */
  --color-der: #8B9EA8;
  --color-die: #C49FA2;
  --color-das: #A8B5A0;
  --color-verb: #B5AFA8;
  --color-adj: #A899B5;

  --card-shadow: 0 24px 48px -12px rgba(45, 41, 38, 0.2);
  --glass-bg: rgba(254, 252, 249, 0.8);
}

@media (prefers-color-scheme: dark) {
  :root {
    /* Dark Mode - Cool Charcoal */
    --bg-color: #121416;
    --surface-color: #1B1D1F;
    --text-main: #ECEFF1;
    --text-muted: #909A9E;
    --primary: #D1C7B7;

    /* POS Colors Dark */
    --color-der: #3A454D;
    --color-die: #4B3739;
    --color-das: #3A4537;
    --color-verb: #3A3835;
    --color-adj: #4B4055;

    --card-shadow: 0 24px 48px -12px rgba(0, 0, 0, 0.6);
    --glass-bg: rgba(28, 26, 23, 0.8);
  }
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Inter", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-main);
  line-height: 1.6;
  overflow-x: hidden;
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* Navigation & Language Toggle */
.top-nav {
  display: flex;
  justify-content: flex-end;
  padding: 1.5rem 2rem 0;
}

.lang-toggle {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.9rem;
}

.lang-toggle button {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-family: inherit;
  font-weight: 500;
  transition: color 0.2s ease;
}

.lang-toggle button.active {
  color: var(--text-main);
  font-weight: 700;
}

.lang-toggle .divider {
  color: var(--text-muted);
  opacity: 0.5;
}

/* ATLAS Style Typography */
.atlas-label {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-muted);
}

header {
  padding: 1rem 2rem 2rem;
  text-align: center;
}

header h1 {
  font-size: 2.5rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 0.5rem;
}

header p.slogan {
  font-size: 1.2rem;
  font-weight: 500;
  color: var(--text-muted);
}

/* Container */
.container {
  max-width: 1000px;
  margin: 0 auto;
  padding: 0 2rem;
}

/* Swiper Section */
.swiper-section {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  margin: 2rem 0 4rem;
  position: relative;
  height: 450px;
}



/* Cards Container */
.cards-container {
  position: relative;
  width: 320px;
  height: 420px;
  perspective: 1000px;
}

.vocab-card {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: var(--surface-color);
  border-radius: 24px;
  box-shadow: none; /* Removed default shadow */
  cursor: grab;
  user-select: none;
  transform-origin: 50% 100%;
  transition: transform 0.5s cubic-bezier(0.34, 1.56, 0.64, 1), opacity 0.3s ease;
  touch-action: none;
  perspective: 1000px;
  background-color: transparent !important;
}

.vocab-card:active {
  cursor: grabbing;
}

/* Only apply shadow to top 2 cards in the stack to prevent dark overlapping blobs */
.vocab-card:nth-last-child(-n+2) {
  box-shadow: var(--card-shadow);
}

.vocab-card.dragging {
  /* Disable transform transition during dragging to prevent lag/stuck issues, but keep a tiny bit of smoothing for the scale effect */
  transition: transform 0.05s ease-out, opacity 0.3s ease, box-shadow 0.3s ease;
  box-shadow: 0 12px 24px -8px var(--card-shadow);
}

/* 3D Flip Styles */
.card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transition: transform 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
  transform-style: preserve-3d;
  border-radius: 24px;
}

.vocab-card.is-flipped .card-inner {
  transform: rotateY(180deg);
}

.card-front, .card-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: 2rem;
  border-radius: 24px;
  background-color: var(--surface-color);
  box-sizing: border-box;
}

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

/* Card POS Colors */
.vocab-card[data-pos="der"] .card-front, .vocab-card[data-pos="der"] .card-back { background-color: var(--color-der); color: #fff; }
.vocab-card[data-pos="die"] .card-front, .vocab-card[data-pos="die"] .card-back { background-color: var(--color-die); color: #fff; }
.vocab-card[data-pos="das"] .card-front, .vocab-card[data-pos="das"] .card-back { background-color: var(--color-das); color: #fff; }
.vocab-card[data-pos="verb"] .card-front, .vocab-card[data-pos="verb"] .card-back { background-color: var(--color-verb); color: #fff; }
.vocab-card[data-pos="adj"] .card-front, .vocab-card[data-pos="adj"] .card-back { background-color: var(--color-adj); color: #fff; }

.vocab-card[data-pos] .atlas-label,
.vocab-card[data-pos] .card-translated,
.vocab-card[data-pos] .card-forms {
  color: rgba(255, 255, 255, 0.8);
}

.card-word {
  font-size: 2rem;
  font-weight: 800;
  margin: 0.5rem 0;
}

.card-translated {
  font-size: 1.25rem;
  font-weight: 500;
  margin-bottom: 1rem;
}

.card-forms {
  font-size: 0.9rem;
  font-style: italic;
  margin-top: auto;
  opacity: 0.9;
}

/* Features Grid */
.features-section {
  margin: 4rem 0;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
}

.feature-card {
  background-color: var(--glass-bg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  padding: 2rem;
  border-radius: 20px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.05);
}

.feature-card h3 {
  font-size: 1.25rem;
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.feature-card p {
  color: var(--text-muted);
  font-size: 0.95rem;
}

.pos-dots {
  display: flex;
  gap: 0.5rem;
  margin-top: 1rem;
}

.dot {
  width: 12px;
  height: 12px;
  border-radius: 50%;
}
.dot.der { background-color: var(--color-der); }
.dot.die { background-color: var(--color-die); }
.dot.das { background-color: var(--color-das); }
.dot.verb { background-color: var(--color-verb); }
.dot.adj { background-color: var(--color-adj); }

footer {
  text-align: center;
  padding: 3rem;
  color: var(--text-muted);
  font-size: 0.85rem;
}

footer a {
  color: var(--primary);
  text-decoration: none;
}

@media (max-width: 600px) {
  .cards-container {
    width: 280px;
    height: 380px;
  }
}

/* Download Button Styles */
.download-btn {
  display: inline-flex;
  align-items: center;
  background-color: var(--text-main);
  color: var(--surface-color);
  padding: 8px 24px;
  border-radius: 14px;
  text-decoration: none;
  margin-top: 2rem;
  transition: transform 0.2s cubic-bezier(0.34, 1.56, 0.64, 1), box-shadow 0.2s ease;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
  z-index: 10;
  position: relative;
}

.download-btn:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.2);
}

.play-icon {
  width: 1.8em;
  height: 1.8em;
  margin-right: 0.8em;
}

.btn-text {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

.btn-text .small-txt {
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  opacity: 0.85;
  line-height: 1;
  margin-bottom: 2px;
}

.btn-text .big-txt {
  font-size: 1.25rem;
  font-weight: 600;
  line-height: 1.1;
  letter-spacing: -0.5px;
}