/* ── Design tokens ─────────────────────────────────────────────────────────── */
:root {
  --bg:           #f8f7f4;
  --surface:      #ffffff;
  --surface-2:    #f2f0eb;
  --text:         #1a1a1a;
  --text-muted:   #6b6b6b;
  --accent:       #2d6a4f;
  --accent-dark:  #1b4332;
  --accent-light: #d8f3dc;
  --border:       #e0ddd6;
  --danger:       #c0392b;
  --danger-light: #fdecea;
  --known:        #27ae60;
  --learning:     #e67e22;
  --dont-know:    #e74c3c;

  --shadow-sm:    0 1px 3px rgba(0,0,0,.08);
  --shadow:       0 4px 12px rgba(0,0,0,.10);
  --shadow-lg:    0 8px 28px rgba(0,0,0,.13);

  --radius:       14px;
  --radius-sm:    8px;
  --radius-xs:    5px;

  --font-heading: 'Playfair Display', Georgia, serif;
  --font-body:    'Inter', 'Noto Sans Bengali', system-ui, sans-serif;
}

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

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.6;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ── Header ────────────────────────────────────────────────────────────────── */
.site-header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-sm);
}

.header-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: .9rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.site-logo {
  font-family: var(--font-heading);
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--accent-dark);
  text-decoration: none;
}

.header-nav {
  display: flex;
  align-items: center;
  gap: .75rem;
}

.student-greeting {
  font-size: .875rem;
  color: var(--text-muted);
}

/* ── Main layout ───────────────────────────────────────────────────────────── */
.main-content {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2.5rem 1.5rem 4rem;
}

/* ── Flash messages ────────────────────────────────────────────────────────── */
.flash-container { margin-bottom: 1.5rem; }

.flash-message {
  background: var(--accent-light);
  color: var(--accent-dark);
  border: 1px solid #b7e4c7;
  border-radius: var(--radius-sm);
  padding: .75rem 1rem;
  font-size: .9rem;
  margin-bottom: .5rem;
}

.flash-error {
  background: var(--danger-light);
  color: var(--danger);
  border-color: #f5c6cb;
}

/* ── Buttons ───────────────────────────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: .4rem;
  font-family: var(--font-body);
  font-size: .9rem;
  font-weight: 500;
  padding: .6rem 1.25rem;
  border-radius: var(--radius-sm);
  border: 1.5px solid transparent;
  cursor: pointer;
  text-decoration: none;
  transition: background .15s, transform .1s, box-shadow .15s;
  white-space: nowrap;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn:active { transform: translateY(0); }

.btn-primary {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.btn-primary:hover { background: var(--accent-dark); border-color: var(--accent-dark); }

.btn-secondary {
  background: var(--surface-2);
  color: var(--text);
  border-color: var(--border);
}
.btn-secondary:hover { background: var(--border); }

.btn-ghost {
  background: transparent;
  color: var(--text-muted);
  border-color: var(--border);
}
.btn-ghost:hover { background: var(--surface-2); color: var(--text); }

.btn-danger {
  background: var(--danger-light);
  color: var(--danger);
  border-color: #f5c6cb;
}
.btn-danger:hover { background: var(--danger); color: #fff; border-color: var(--danger); }

.btn-sm { font-size: .8rem; padding: .4rem .9rem; }
.btn-full { width: 100%; }

.btn-known {
  background: var(--known);
  color: #fff;
  border-color: var(--known);
  font-size: 1rem;
  padding: .8rem 2rem;
}
.btn-known:hover { background: #219a52; border-color: #219a52; }

.btn-dont-know {
  background: #fdecea;
  color: var(--dont-know);
  border-color: #f5c6cb;
  font-size: 1rem;
  padding: .8rem 2rem;
}
.btn-dont-know:hover { background: var(--dont-know); color: #fff; border-color: var(--dont-know); }

/* ── Forms ─────────────────────────────────────────────────────────────────── */
.form-group { margin-bottom: 1.25rem; }

.form-label {
  display: block;
  font-size: .85rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: .04em;
  margin-bottom: .4rem;
}

.required { color: var(--danger); }

.form-input {
  width: 100%;
  padding: .7rem 1rem;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: var(--font-body);
  font-size: .95rem;
  color: var(--text);
  background: var(--surface);
  transition: border-color .15s, box-shadow .15s;
  outline: none;
}
.form-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(45,106,79,.12);
}
.form-textarea { resize: vertical; min-height: 80px; }
.form-select { appearance: none; cursor: pointer; }
.form-input-sm { max-width: 120px; }

.form-hint {
  font-size: .8rem;
  color: var(--text-muted);
  margin-top: .35rem;
}

.form-actions {
  display: flex;
  gap: .75rem;
  padding-top: .5rem;
}

/* ── Auth pages ────────────────────────────────────────────────────────────── */
.auth-page {
  min-height: 70vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

.auth-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 2.5rem 2rem;
  width: 100%;
  max-width: 420px;
}

.auth-title {
  font-family: var(--font-heading);
  font-size: 1.75rem;
  color: var(--accent-dark);
  margin-bottom: .4rem;
  text-align: center;
}

.auth-subtitle {
  font-size: .9rem;
  color: var(--text-muted);
  text-align: center;
  margin-bottom: 1.75rem;
}

.auth-form { display: flex; flex-direction: column; gap: .5rem; }

/* ── Page header ───────────────────────────────────────────────────────────── */
.page-header { margin-bottom: 2rem; }
.page-title {
  font-family: var(--font-heading);
  font-size: 2rem;
  color: var(--accent-dark);
  margin-bottom: .25rem;
}
.page-subtitle { color: var(--text-muted); font-size: .95rem; }

/* ── Sections grid ─────────────────────────────────────────────────────────── */
.sections-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1.25rem;
}

.section-card {
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  text-decoration: none;
  color: var(--text);
  display: flex;
  flex-direction: column;
  gap: 1rem;
  box-shadow: var(--shadow-sm);
  transition: box-shadow .2s, transform .2s, border-color .2s;
}
.section-card:hover {
  box-shadow: var(--shadow);
  transform: translateY(-3px);
  border-color: var(--accent);
  text-decoration: none;
}

.section-name {
  font-family: var(--font-heading);
  font-size: 1.2rem;
  color: var(--accent-dark);
}
.section-count { font-size: .85rem; color: var(--text-muted); }

/* ── Progress bars ─────────────────────────────────────────────────────────── */
.progress-bars { display: flex; flex-direction: column; gap: .45rem; }

.progress-row { display: flex; flex-direction: column; gap: .25rem; }

.progress-bar-wrap {
  height: 8px;
  background: var(--surface-2);
  border-radius: 99px;
  overflow: hidden;
}
.progress-bar-fill {
  height: 100%;
  background: var(--accent);
  border-radius: 99px;
  transition: width .4s ease;
}
.progress-bar-fill.learning-fill {
  background: var(--learning);
}
.progress-bar-fill.dont-know-fill {
  background: var(--dont-know);
}
.progress-label {
  font-size: .78rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: .35rem;
}
.progress-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
}
.progress-dot.dot-known     { background: var(--accent); }
.progress-dot.dot-learning  { background: var(--learning); }
.progress-dot.dot-dont-know { background: var(--dont-know); }

/* ── Flashcard page ────────────────────────────────────────────────────────── */
.flashcard-page { max-width: 680px; margin: 0 auto; }

.flashcard-header {
  margin-bottom: 2rem;
}
.back-link {
  font-size: .85rem;
  color: var(--text-muted);
  display: inline-block;
  margin-bottom: .75rem;
}
.back-link:hover { color: var(--accent); }

.section-title {
  font-family: var(--font-heading);
  font-size: 1.6rem;
  color: var(--accent-dark);
  margin-bottom: .75rem;
}

.session-progress { margin-top: .5rem; }

.deck-counter {
  text-align: center;
  font-size: .85rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

/* ── Flashcard flip ────────────────────────────────────────────────────────── */
.card-scene {
  perspective: 1000px;
  margin-bottom: 1.5rem;
}

.flashcard {
  width: 100%;
  min-height: 280px;
  position: relative;
  transform-style: preserve-3d;
  transition: transform .5s cubic-bezier(.4,0,.2,1);
  cursor: pointer;
}
.flashcard.is-flipped { transform: rotateY(180deg); cursor: default; }

.card-face {
  position: absolute;
  inset: 0;
  border-radius: var(--radius);
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2.5rem 2rem;
  background: var(--surface);
  border: 1.5px solid var(--border);
}

.card-front { background: var(--surface); }
.card-back {
  transform: rotateY(180deg);
  align-items: flex-start;
  justify-content: flex-start;
  overflow-y: auto;
  max-height: 420px;
}

.card-word {
  font-family: var(--font-heading);
  font-size: 2.2rem;
  font-weight: 700;
  color: var(--accent-dark);
  text-align: center;
  margin-bottom: .75rem;
}
.card-hint { font-size: .85rem; color: var(--text-muted); }

/* Streak progress badge on card front */
.streak-badge {
  position: absolute;
  top: 1rem;
  right: 1rem;
  background: var(--accent-light);
  color: var(--accent-dark);
  font-size: .75rem;
  font-weight: 700;
  border-radius: 99px;
  padding: .2rem .65rem;
  letter-spacing: .03em;
}

.card-back-content { width: 100%; }
.card-section { margin-bottom: 1rem; }
.card-section:last-child { margin-bottom: 0; }
.card-label {
  display: inline-block;
  font-size: .68rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .07em;
  color: var(--accent-dark);
  background: var(--accent-light);
  border-radius: 99px;
  padding: .22rem .75rem;
  margin-bottom: .55rem;
}
.card-text {
  font-size: 1.08rem;
  color: var(--text);
  line-height: 1.65;
  white-space: pre-line;
}

/* Word heading on the back face */
.card-back-word {
  font-family: var(--font-heading);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent-dark);
  width: 100%;
  margin-bottom: 1.25rem;
  padding-bottom: .75rem;
  border-bottom: 1.5px solid var(--border);
}

/* Green highlight for the studied word inside example sentences */
.word-highlight {
  color: var(--known);
  font-weight: 700;
  background: var(--accent-light);
  border-radius: 3px;
  padding: 0 3px;
}

/* ── Card action buttons ───────────────────────────────────────────────────── */
.card-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
  opacity: 0;
  transform: translateY(8px);
  transition: opacity .25s, transform .25s;
  pointer-events: none;
}
.card-actions.is-visible {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}

/* ── Completion screen ─────────────────────────────────────────────────────── */
.completion-screen {
  display: flex;
  justify-content: center;
  padding: 2rem 0;
}
.completion-card {
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 3rem 2.5rem;
  text-align: center;
  max-width: 480px;
  width: 100%;
}
.completion-icon { font-size: 3.5rem; margin-bottom: 1rem; }
.completion-title {
  font-family: var(--font-heading);
  font-size: 1.75rem;
  color: var(--accent-dark);
  margin-bottom: .75rem;
}
.completion-stats { color: var(--text-muted); margin-bottom: 2rem; }
.completion-actions { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; }

/* ── Empty state ───────────────────────────────────────────────────────────── */
.empty-state {
  text-align: center;
  padding: 3rem 1.5rem;
  color: var(--text-muted);
  background: var(--surface);
  border: 1.5px dashed var(--border);
  border-radius: var(--radius);
}

/* ── Responsive ────────────────────────────────────────────────────────────── */
@media (max-width: 600px) {
  .main-content { padding: 1.5rem 1rem 3rem; }
  .sections-grid { grid-template-columns: 1fr; }
  .card-word { font-size: 1.75rem; }
  .card-actions { flex-direction: column; }
  .btn-known, .btn-learning { width: 100%; justify-content: center; }
  .completion-actions { flex-direction: column; }
  .auth-card { padding: 2rem 1.25rem; }
}