:root {
  --bg-body: #0A0F1D;
  --bg-card: #111827;
  --bg-tile: #1E293B;
  --border-main: #374151;
  --color-primary: #6366F1;
  --color-primary-dark: #4F46E5;
  --color-success: #10B981;
  --color-error: #EF4444;
  --color-warning: #F59E0B;
  --color-cyan: #06B6D4;
  --text-main: #F3F4F6;
  --text-muted: #9CA3AF;
  --radius-card: 16px;
  --font-family: 'Plus Jakarta Sans', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
}

* { box-sizing: border-box; margin: 0; padding: 0; -webkit-tap-highlight-color: transparent; }
body {
  background-color: var(--bg-body);
  color: var(--text-main);
  font-family: var(--font-family);
  min-height: 100dvh;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  overflow-x: hidden;
}

#app-container {
  width: 100%;
  min-height: 100dvh;
  background-color: var(--bg-card);
  display: flex;
  flex-direction: column;
  position: relative;
}

@media (min-width: 501px) {
  #app-container {
    max-width: 460px;
    margin: 16px auto;
    min-height: calc(100dvh - 32px);
    border: 1px solid var(--border-main);
    border-radius: var(--radius-card);
    box-shadow: 0 16px 48px rgba(0, 0, 0, 0.6);
    overflow: hidden;
  }
}

/* Header */
#app-header {
  min-height: calc(58px + env(safe-area-inset-top, 0px));
  padding: env(safe-area-inset-top, 0px) 14px 0 14px;
  background: rgba(17, 24, 39, 0.95);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-main);
  display: flex;
  align-items: center;
  justify-content: space-between;
  position: sticky;
  top: 0;
  z-index: 50;
}
.header-left, .header-right { display: flex; align-items: center; gap: 8px; }
#header-brand { font-weight: 800; font-size: 15px; color: var(--color-primary); letter-spacing: -0.3px; }
#header-subtitle { font-size: 11px; color: var(--text-muted); display: block; font-weight: 500; }
.stat-pill { background: var(--bg-tile); border: 1px solid var(--border-main); padding: 4px 8px; border-radius: 20px; font-size: 12px; font-weight: 700; display: flex; align-items: center; gap: 4px; }
.profile-btn { background: #312E81; border: 1px solid #4F46E5; color: var(--text-main); padding: 4px 10px; border-radius: 20px; font-size: 11px; font-weight: 600; cursor: pointer; max-width: 120px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }


/* Progress bar */
#step-progress-bar { height: 6px; background: var(--bg-tile); width: 100%; }
#step-progress-fill { height: 100%; background: linear-gradient(90deg, var(--color-primary), var(--color-cyan)); transition: width 0.3s ease; }

/* Main Content Area */
#main-content {
  flex: 1;
  padding: 16px 16px calc(20px + env(safe-area-inset-bottom, 0px)) 16px;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
}

/* Buttons */
.btn-primary, .btn-success, .btn-warning, .btn-ghost, .btn-sub {
  font-family: var(--font-family);
  font-weight: 700;
  font-size: 14px;
  padding: 12px 18px;
  border-radius: 12px;
  border: none;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  transition: all 0.15s ease;
  user-select: none;
}
.btn-primary { background: var(--color-primary); color: #fff; box-shadow: 0 4px 0 var(--color-primary-dark); }
.btn-primary:active { transform: translateY(3px); box-shadow: 0 1px 0 var(--color-primary-dark); }
.btn-success { background: var(--color-success); color: #fff; box-shadow: 0 4px 0 #059669; }
.btn-success:active { transform: translateY(3px); box-shadow: 0 1px 0 #059669; }
.btn-warning { background: var(--color-warning); color: #000; box-shadow: 0 4px 0 #D97706; }
.btn-ghost { background: transparent; color: var(--text-muted); border: 1px solid var(--border-main); }
.btn-sub { background: var(--bg-tile); color: var(--text-main); border: 1px solid var(--border-main); padding: 8px 12px; }
.icon-btn { background: none; border: none; color: var(--text-main); cursor: pointer; padding: 6px; border-radius: 8px; display: flex; align-items: center; }

/* Audio Pill Buttons (1.0x & 0.75x) */
.btn-audio-pill {
  font-family: var(--font-family);
  font-weight: 700;
  font-size: 13px;
  padding: 8px 16px;
  min-width: 112px;
  border-radius: 999px;
  background: #0F172A;
  color: var(--text-main);
  border: 1.5px solid #334155;
  box-shadow: 0 2px 0 #090D16;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  transition: all 0.18s ease;
  user-select: none;
}
.btn-audio-pill:hover { border-color: var(--color-primary); background: #1E293B; transform: translateY(-1px); }
.btn-audio-pill:active { transform: translateY(1px); box-shadow: none; }
.btn-audio-pill.speed-normal { border-color: rgba(99, 102, 241, 0.55); color: #E0E7FF; }
.btn-audio-pill.speed-slow { border-color: rgba(245, 158, 11, 0.45); color: #FEF3C7; }


/* Roadmap Timeline */
.roadmap-container { display: flex; flex-direction: column; gap: 14px; }
.unit-card {
  background: var(--bg-tile);
  border: 1px solid var(--border-main);
  border-radius: 14px;
  padding: 14px;
  cursor: pointer;
  transition: transform 0.15s, border-color 0.15s;
}
.unit-card:hover { transform: translateY(-2px); border-color: var(--color-primary); }
.unit-card.active { border-color: var(--color-primary); box-shadow: 0 0 16px rgba(99, 102, 241, 0.2); }
.unit-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 6px; }
.unit-badge { font-size: 10px; font-weight: 800; padding: 3px 8px; border-radius: 6px; background: rgba(99,102,241,0.2); color: #818CF8; }
.unit-title { font-size: 15px; font-weight: 700; color: var(--text-main); margin-bottom: 4px; }
.unit-sub { font-size: 12px; color: var(--text-muted); }

/* Timeline Steps in UnitPath */
.timeline-path { display: flex; flex-direction: column; align-items: center; gap: 14px; padding: 12px 0; }
.step-node {
  width: 64px;
  height: 64px;
  border-radius: 50%;
  background: var(--bg-tile);
  border: 3px solid var(--border-main);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.2s;
  position: relative;
}
.step-node.completed { background: #064E3B; border-color: var(--color-success); }
.step-node.current { border-color: var(--color-primary); box-shadow: 0 0 20px var(--color-primary); transform: scale(1.08); }
.step-node-icon { font-size: 22px; }
.step-node-lbl { font-size: 9px; font-weight: 700; color: var(--text-muted); margin-top: 2px; }

/* Flashcard */
.flashcard {
  background: var(--bg-tile);
  border: 1px solid var(--border-main);
  border-radius: var(--radius-card);
  padding: 24px 18px;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}
.fc-word { font-size: 32px; font-weight: 800; color: var(--text-main); }
.fc-ipa { font-size: 16px; color: var(--color-cyan); font-family: var(--font-mono); }
.fc-meaning { font-size: 17px; font-weight: 600; color: var(--color-warning); }
.fc-example-box {
  background: #0F172A;
  border: 1px solid #334155;
  border-radius: 10px;
  padding: 10px 14px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  font-style: italic;
  color: #E2E8F0;
  transition: background 0.15s;
}
.fc-example-box:hover { background: #1E293B; }
.audio-ctrl-row { display: flex; gap: 8px; justify-content: center; flex-wrap: wrap; align-items: center; }

/* Chart Builder */
.chart-challenge-box { background: rgba(99,102,241,0.12); border: 1px solid #4F46E5; border-radius: 10px; padding: 10px 12px; font-size: 13px; margin-bottom: 12px; }
.chart-columns { display: grid; grid-template-columns: repeat(auto-fit, minmax(80px, 1fr)); gap: 8px; margin: 12px 0; }
.chart-col { background: #0F172A; border: 1px solid #334155; border-radius: 10px; padding: 8px; }
.chart-col-title { font-size: 10px; font-weight: 700; color: var(--color-cyan); text-transform: uppercase; margin-bottom: 6px; }
.chart-opt-btn { width: 100%; padding: 8px 4px; font-size: 12px; font-weight: 600; border-radius: 6px; background: var(--bg-tile); border: 1px solid #334155; color: var(--text-main); margin-bottom: 4px; cursor: pointer; }
.chart-opt-btn.selected { background: var(--color-primary); border-color: #818CF8; }
.chart-preview-box { border-radius: 10px; padding: 12px; text-align: center; font-size: 16px; font-weight: 700; margin: 10px 0; }
.chart-preview-box.valid { background: rgba(16,185,129,0.15); border: 1px solid var(--color-success); color: var(--color-success); }
.chart-preview-box.invalid { background: rgba(239,68,68,0.15); border: 1px solid var(--color-error); color: var(--color-error); }
.chart-preview-box.selecting { background: #0F172A; border: 1px dashed #475569; color: var(--text-muted); }

/* Scramble Word Tiles */
.scramble-slots { min-height: 52px; border: 2px dashed #475569; border-radius: 12px; padding: 8px; display: flex; flex-wrap: wrap; gap: 8px; margin: 12px 0; align-items: center; justify-content: center; }
.word-tile {
  background: var(--bg-tile);
  border: 1px solid var(--border-main);
  box-shadow: 0 3px 0 var(--border-main);
  padding: 8px 14px;
  border-radius: 10px;
  font-weight: 700;
  font-size: 15px;
  cursor: pointer;
  user-select: none;
  transition: all 0.1s;
}
.word-tile:active { transform: translateY(2px); box-shadow: 0 1px 0 var(--border-main); }
.word-tile.picked { opacity: 0.25; pointer-events: none; }

/* Quiz Choice / Cross-out */
.quiz-options { display: flex; flex-direction: column; gap: 10px; margin: 16px 0; }
.quiz-opt-btn { background: var(--bg-tile); border: 2px solid var(--border-main); border-radius: 12px; padding: 14px 16px; font-size: 15px; font-weight: 600; color: var(--text-main); text-align: left; cursor: pointer; transition: all 0.15s; display: flex; justify-content: space-between; align-items: center; }
.quiz-opt-btn.selected { border-color: var(--color-primary); background: rgba(99,102,241,0.12); }
.quiz-opt-btn.crossed { text-decoration: line-through; opacity: 0.6; }
.quiz-feedback-banner { padding: 14px; border-radius: 12px; margin-top: 14px; font-size: 14px; }
.quiz-feedback-banner.correct { background: rgba(16,185,129,0.18); border: 1px solid var(--color-success); color: #34D399; }
.quiz-feedback-banner.wrong { background: rgba(239,68,68,0.18); border: 1px solid var(--color-error); color: #F87171; }

/* Modals */
.modal-backdrop { position: fixed; inset: 0; background: rgba(0,0,0,0.75); display: flex; align-items: center; justify-content: center; z-index: 100; padding: 16px; }
.modal-card { background: var(--bg-card); border: 1px solid var(--border-main); border-radius: var(--radius-card); width: 100%; max-width: 400px; padding: 20px; box-shadow: 0 20px 60px rgba(0,0,0,0.7); }
.modal-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 14px; }
.modal-body { display: flex; flex-direction: column; gap: 10px; }
.modal-footer { display: flex; justify-content: flex-end; gap: 10px; margin-top: 16px; }
.profile-stat-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; margin-bottom: 8px; }
.p-stat-box { background: var(--bg-tile); border: 1px solid var(--border-main); border-radius: 10px; padding: 10px; text-align: center; }
.p-val { font-size: 18px; font-weight: 800; color: var(--color-primary); display: block; }
.p-lbl { font-size: 10px; color: var(--text-muted); }
.form-input { background: var(--bg-tile); border: 1px solid var(--border-main); color: var(--text-main); padding: 10px 12px; border-radius: 8px; font-size: 13px; font-family: var(--font-family); }
.form-label { font-size: 12px; font-weight: 600; color: var(--text-muted); }
.uuid-row { display: flex; gap: 6px; }
.uuid-row .form-input { flex: 1; font-family: var(--font-mono); font-size: 11px; }
.modal-hint { font-size: 11px; color: var(--color-cyan); line-height: 1.4; }
.sim-btn-list { display: flex; flex-direction: column; gap: 8px; margin-top: 10px; }
.spinner { width: 36px; height: 36px; border: 4px solid var(--bg-tile); border-top-color: var(--color-primary); border-radius: 50%; animation: spin 0.8s linear infinite; margin: 40px auto 14px; }
.loading-spinner-box { text-align: center; color: var(--text-muted); font-size: 13px; }
@keyframes spin { to { transform: rotate(360deg); } }

/* Shadowing Word Tokens & Evaluation Chips */
.shadow-word-token { display: inline-block; padding: 2px 5px; margin: 1px; border-radius: 6px; border-bottom: 2px dotted rgba(148, 163, 184, 0.45); cursor: pointer; transition: all 0.15s ease; }
.shadow-word-token:hover { background: rgba(99, 102, 241, 0.2); border-bottom-color: var(--color-cyan); transform: translateY(-1px); }
.eval-word-chip { cursor: pointer; display: inline-flex; align-items: center; gap: 4px; transition: transform 0.15s; }
.eval-word-chip:hover { transform: scale(1.05); filter: brightness(1.2); }

/* Audio Playing Visual State Feedback */
.audio-playing { background: #0E7490 !important; border-color: #22D3EE !important; color: #FFFFFF !important; animation: audioPulse 1.1s infinite ease-in-out !important; }
@keyframes audioPulse {
  0% { box-shadow: 0 0 0 0 rgba(34, 211, 238, 0.65); }
  70% { box-shadow: 0 0 0 10px rgba(34, 211, 238, 0); }
  100% { box-shadow: 0 0 0 0 rgba(34, 211, 238, 0); }
}