:root {
  --font-display: 'Inter', -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Noto Sans SC', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', Menlo, monospace;
  --fg: #0F172A;
  --fg-soft: #F1F5F9;
  --muted: #94A3B8;
  --radius: 10px;
  --radius-lg: 16px;
  --accent-soft: #EEF2FF;
  --success-soft: #D1FAE5;
  --warning-soft: #FEF3C7;
  --accent: #4F46E5;
  --surface: #FFFFFF;
  --border: #E2E8F0;
  --success: #10B981;
  --danger: #EF4444;
  --warning: #F59E0B;
  --shadow: rgba(79, 70, 229, 0.12);
}

body {
  margin: 0;
  background: #F8FAFC;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.app-screen {
  max-width: 430px;
  margin: 0 auto;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background: var(--surface);
  position: relative;
}

.app-header {
  display: flex;
  align-items: center;
  padding: 12px 16px;
  padding-top: max(12px, env(safe-area-inset-top, 12px));
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  gap: 8px;
}

.app-header-back {
  width: 36px;
  height: 36px;
  display: grid;
  place-items: center;
  border: none;
  background: var(--fg-soft);
  border-radius: 50%;
  cursor: pointer;
  color: var(--fg);
  flex-shrink: 0;
  transition: background 0.15s;
}
.app-header-back:active {
  background: var(--border);
}
.app-header-back svg {
  width: 20px;
  height: 20px;
}

.app-header-title {
  flex: 1;
  font-family: var(--font-display);
  font-size: 17px;
  font-weight: 700;
  color: var(--fg);
  text-align: center;
}

.android-topbar {
  display: flex;
  align-items: center;
  padding: 4px 12px 0;
  padding-top: max(4px, env(safe-area-inset-top, 4px));
  background: var(--surface);
}
.android-topbar-icon {
  width: 40px; height: 40px;
  display: grid; place-items: center;
  color: var(--muted);
  border-radius: 50%;
  border: none;
  background: none;
  cursor: pointer;
  flex-shrink: 0;
}
.android-topbar-icon:active { background: var(--fg-soft); }
.android-topbar-icon svg { width: 22px; height: 22px; }
.android-topbar-title {
  flex: 1;
  text-align: center;
  font-family: var(--font-display);
  font-size: 16px;
  font-weight: 600;
  color: var(--fg);
  margin-right: 40px;
}

.app-header-progress {
  display: flex;
  gap: 6px;
  align-items: center;
  flex-shrink: 0;
}

.progress-dot {
  width: 8px;
  height: 8px;
  border-radius: 4px;
  background: var(--border);
  transition: background 0.3s, transform 0.2s;
}
.progress-dot.done {
  background: var(--accent);
}
.progress-dot.active {
  background: var(--accent);
  transform: scale(1.3);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 10px 24px;
  border: none;
  border-radius: var(--radius);
  font-family: var(--font-display);
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.1s, background 0.15s;
}
.btn:active {
  transform: scale(0.96);
}
.btn-primary {
  background: var(--accent);
  color: #fff;
}

.fade-in {
  animation: fadeIn 0.3s ease both;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}