:root {
  --bg: #000000;
  --panel: #070707;
  --panel-2: #0d0d0d;
  --panel-3: #111111;
  --border: #1e1e1e;
  --border-strong: #2b2b2b;
  --text: #f5f5f5;
  --muted: #9a9a9a;
  --shadow: 0 18px 50px rgba(0, 0, 0, 0.45);
  --radius-xl: 24px;
  --radius-lg: 18px;
  --radius-md: 14px;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: 'Inter', system-ui, sans-serif;
  min-height: 100%;
}

body {
  min-height: 100vh;
}

button,
input {
  font: inherit;
}

button {
  cursor: pointer;
}

.app-shell {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 20px;
  padding: 20px;
  background:
    radial-gradient(circle at top left, rgba(255,255,255,0.05), transparent 30%),
    linear-gradient(180deg, #050505 0%, #000000 100%);
}

.sidebar,
.viewer-area {
  background: rgba(8, 8, 8, 0.92);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow);
}

.sidebar {
  padding: 22px;
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 14px;
}

.brand h1,
.brand p {
  margin: 0;
}

.brand h1 {
  font-size: 1.1rem;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.brand p {
  color: var(--muted);
  font-size: 0.86rem;
}

.upload-card,
.dropzone,
.meta-card,
.tips-card {
  background: linear-gradient(180deg, var(--panel-2), var(--panel));
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
}

.upload-card {
  padding: 20px;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 8px;
  cursor: pointer;
  transition: border-color 0.2s ease, transform 0.2s ease, background 0.2s ease;
}

.upload-card:hover,
.dropzone.dragover {
  border-color: var(--border-strong);
  transform: translateY(-1px);
  background: linear-gradient(180deg, #131313, #090909);
}

.upload-icon {
  width: 42px;
  height: 42px;
  border-radius: 12px;
  display: grid;
  place-items: center;
  font-size: 1.4rem;
  background: #ffffff;
  color: #000000;
  font-weight: 700;
}

.upload-card small,
.dropzone small,
.tips-card li,
.meta-row span {
  color: var(--muted);
}

.dropzone {
  padding: 18px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  border-style: dashed;
}

.meta-card,
.tips-card {
  padding: 18px;
}

.meta-row {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 0;
  border-bottom: 1px solid #151515;
}

.meta-row:last-child {
  border-bottom: 0;
}

.meta-row strong {
  text-align: right;
  max-width: 160px;
  word-break: break-word;
}

.tips-card strong {
  display: block;
  margin-bottom: 10px;
}

.tips-card ul {
  margin: 0;
  padding-left: 18px;
  display: grid;
  gap: 8px;
}

.viewer-area {
  display: grid;
  grid-template-rows: auto 1fr;
  overflow: hidden;
}

.topbar {
  padding: 18px 20px;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
  background: rgba(10, 10, 10, 0.9);
}

.toolbar-group {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.tool-btn,
.page-box {
  background: linear-gradient(180deg, #141414, #0b0b0b);
  border: 1px solid var(--border-strong);
  color: var(--text);
  border-radius: 12px;
}

.tool-btn {
  min-width: 82px;
  padding: 11px 14px;
  transition: transform 0.15s ease, border-color 0.2s ease, background 0.2s ease;
}

.tool-btn:hover {
  transform: translateY(-1px);
  border-color: #404040;
  background: linear-gradient(180deg, #191919, #101010);
}

.page-box {
  padding: 10px 12px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.page-box input {
  width: 64px;
  background: transparent;
  border: 0;
  color: var(--text);
  outline: none;
}

.tool-stat {
  min-width: 56px;
  text-align: center;
  color: var(--muted);
  font-weight: 600;
}

.viewer-panel {
  position: relative;
  overflow: auto;
  background:
    linear-gradient(180deg, rgba(255,255,255,0.02), rgba(255,255,255,0.01)),
    #050505;
}

.empty-state {
  min-height: 100%;
  display: grid;
  place-items: center;
  padding: 30px;
}

.empty-frame {
  width: min(640px, 100%);
  min-height: 320px;
  border-radius: 30px;
  border: 1px dashed #262626;
  background: linear-gradient(180deg, rgba(255,255,255,0.025), rgba(255,255,255,0.01));
  display: grid;
  place-items: center;
  text-align: center;
  padding: 32px;
}

.empty-frame h2 {
  margin: 0 0 10px;
  font-size: clamp(1.6rem, 2vw, 2.3rem);
}

.empty-frame p {
  margin: 0;
  color: var(--muted);
  max-width: 420px;
}

.canvas-wrap {
  display: flex;
  justify-content: center;
  padding: 28px;
}

#pdf-canvas {
  max-width: 100%;
  height: auto;
  border-radius: 16px;
  box-shadow: 0 22px 70px rgba(0,0,0,0.55);
  background: white;
}

.hidden {
  display: none !important;
}

@media (max-width: 980px) {
  .app-shell {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .app-shell {
    padding: 14px;
    gap: 14px;
  }

  .sidebar,
  .viewer-area {
    border-radius: 20px;
  }

  .topbar,
  .sidebar {
    padding: 16px;
  }

  .tool-btn {
    min-width: 70px;
  }
}