:root {
  --background: 222 100% 98%;
  --foreground: 226 38% 16%;
  --primary: 262 83% 58%;
  --secondary: 188 82% 45%;
  --muted: 220 35% 94%;
  --destructive: 0 78% 58%;
  --border: 224 28% 86%;
  --card: 0 0% 100%;

  --shadow-sm: 0 6px 18px hsla(262, 83%, 58%, 0.08);
  --shadow-md: 0 14px 32px hsla(230, 50%, 20%, 0.12);
  --shadow-lg: 0 24px 60px hsla(262, 83%, 58%, 0.18);

  --transition-fast: 160ms ease;
  --transition-smooth: 280ms cubic-bezier(0.22, 1, 0.36, 1);

  --radius-sm: 0.75rem;
  --radius-md: 1rem;
  --radius-lg: 1.5rem;
}

.dark {
  --background: 229 35% 10%;
  --foreground: 220 33% 96%;
  --primary: 268 100% 72%;
  --secondary: 188 78% 54%;
  --muted: 230 24% 18%;
  --destructive: 0 82% 64%;
  --border: 228 18% 24%;
  --card: 228 26% 14%;

  --shadow-sm: 0 6px 18px hsla(268, 100%, 72%, 0.12);
  --shadow-md: 0 14px 32px hsla(0, 0%, 0%, 0.24);
  --shadow-lg: 0 24px 60px hsla(268, 100%, 72%, 0.2);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at top left, hsla(262, 83%, 58%, 0.14), transparent 32%),
    radial-gradient(circle at top right, hsla(188, 82%, 45%, 0.14), transparent 26%),
    hsl(var(--background));
}

a,
button,
input,
select {
  transition: all var(--transition-fast);
}

button:focus-visible,
a:focus-visible,
input:focus-visible,
select:focus-visible {
  outline: 3px solid hsla(262, 83%, 58%, 0.26);
  outline-offset: 2px;
}

.card-surface {
  background: hsl(var(--card));
  border: 1px solid hsl(var(--border));
  box-shadow: var(--shadow-md);
}

.glass-panel {
  background: linear-gradient(180deg, hsla(0, 0%, 100%, 0.76), hsla(0, 0%, 100%, 0.58));
  backdrop-filter: blur(18px);
}

.dark .glass-panel {
  background: linear-gradient(180deg, hsla(228, 26%, 14%, 0.84), hsla(228, 26%, 14%, 0.72));
}

.note-gradient {
  background:
    linear-gradient(135deg, hsla(262, 83%, 58%, 0.16), hsla(188, 82%, 45%, 0.14)),
    hsl(var(--card));
}

.subject-chip {
  display: inline-flex;
  align-items: center;
  border-radius: 999px;
  border: 1px solid hsla(262, 83%, 58%, 0.16);
  background: hsla(262, 83%, 58%, 0.12);
  color: hsl(var(--primary));
}

.btn-pop:hover {
  transform: translateY(-1px) scale(1.01);
}

.grid-auto {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
}

.pdf-frame {
  width: 100%;
  min-height: 72vh;
  border: 1px solid hsl(var(--border));
  border-radius: var(--radius-lg);
  background: hsl(var(--card));
  box-shadow: var(--shadow-md);
}

@media (max-width: 640px) {
  .pdf-frame {
    min-height: 60vh;
  }
}