:root {
  --bg-0: #eef3ff;
  --bg-1: #f7fbff;
  --body-glow-a: #d5ecff;
  --body-glow-b: #ffe4ce;
  --shape-a: #a6d7ff;
  --shape-b: #ffd2a9;
  --panel: rgba(255, 255, 255, 0.88);
  --panel-strong: #ffffff;
  --input-bg: #ffffff;
  --item-bg: #ffffff;
  --item-selected-bg: #f1f8ff;
  --canvas-grid: #f7faff;
  --canvas-bg: #ffffff;
  --canvas-border: #d2def1;
  --zoom-color: #34527d;
  --tool-active-bg: #e9f4ff;
  --tool-active-border: #97c8f5;
  --tool-active-ink: #0a5696;
  --editor-border: #8cb9e7;
  --editor-border-focus: #3d8de0;
  --editor-bg: rgba(255, 255, 255, 0.95);
  --ink: #0f1d36;
  --muted: #51607a;
  --line: #dbe3f2;
  --brand: #0a75d2;
  --brand-strong: #05579f;
  --accent: #ff8a3d;
  --accent-strong: #de6d21;
  --danger: #b3261e;
  --ok: #176847;
  --radius: 16px;
  --radius-sm: 12px;
  --shadow-lg: 0 22px 50px rgba(17, 52, 103, 0.13);
  --shadow-md: 0 12px 26px rgba(17, 52, 103, 0.08);
}

:root[data-theme="dark"] {
  --bg-0: #101827;
  --bg-1: #111d31;
  --body-glow-a: #1b2f4f;
  --body-glow-b: #2f2520;
  --shape-a: #2b4d7a;
  --shape-b: #5d3f2d;
  --panel: rgba(19, 27, 42, 0.82);
  --panel-strong: #1b2538;
  --input-bg: #162133;
  --item-bg: #172338;
  --item-selected-bg: #21334e;
  --canvas-grid: #172133;
  --canvas-bg: #101827;
  --canvas-border: #2d3d59;
  --zoom-color: #8ca8d1;
  --tool-active-bg: #234167;
  --tool-active-border: #3d6ea8;
  --tool-active-ink: #d5e8ff;
  --editor-border: #4d6e9d;
  --editor-border-focus: #6f9ed8;
  --editor-bg: rgba(18, 29, 45, 0.96);
  --ink: #e2e9f5;
  --muted: #9fb0cd;
  --line: #2b3b58;
  --shadow-md: 0 12px 26px rgba(0, 0, 0, 0.35);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  padding: 1.15rem;
  font-family: "Plus Jakarta Sans", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at 10% 8%, var(--body-glow-a) 0%, transparent 34%),
    radial-gradient(circle at 90% 10%, var(--body-glow-b) 0%, transparent 36%),
    linear-gradient(145deg, var(--bg-0), var(--bg-1));
  transition: background 0.25s ease, color 0.2s ease;
}

.bg-shape {
  position: fixed;
  z-index: -1;
  border-radius: 999px;
  filter: blur(36px);
  opacity: 0.35;
}

.bg-shape-a {
  width: 280px;
  height: 280px;
  top: 6%;
  right: 4%;
  background: var(--shape-a);
}

.bg-shape-b {
  width: 320px;
  height: 320px;
  bottom: 4%;
  left: 5%;
  background: var(--shape-b);
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 0.95rem;
}

.topbar h1 {
  margin: 0;
  font-family: "Sora", sans-serif;
  font-size: clamp(1.35rem, 2.8vw, 2rem);
  letter-spacing: 0.01em;
}

.topbar p {
  margin: 0.28rem 0 0;
  color: var(--muted);
}

.status-pill {
  border: 1px solid var(--line);
  background: var(--panel-strong);
  border-radius: 999px;
  padding: 0.46rem 0.84rem;
  font-size: 0.9rem;
  box-shadow: var(--shadow-md);
}

.card {
  background: var(--panel);
  backdrop-filter: blur(8px);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-md);
}

.toolbar {
  position: sticky;
  top: 0.6rem;
  z-index: 8;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.58rem;
  padding: 0.78rem;
  margin-bottom: 1rem;
  animation: rise 0.38s ease-out;
}

.btn {
  border: 1px solid var(--line);
  border-radius: 11px;
  padding: 0.5rem 0.78rem;
  background: var(--panel-strong);
  color: var(--ink);
  font: inherit;
  font-size: 0.92rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.16s ease, box-shadow 0.2s ease, background 0.2s ease;
}

.btn:hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: 0 8px 18px rgba(24, 61, 118, 0.14);
}

.btn:disabled {
  opacity: 0.58;
  cursor: not-allowed;
}

.btn-primary {
  color: #fff;
  border-color: var(--brand);
  background: linear-gradient(160deg, #1487ea, var(--brand));
}

.btn-primary:hover:not(:disabled) {
  background: linear-gradient(160deg, #0f7ad4, var(--brand-strong));
}

.btn-accent {
  color: #fff;
  border-color: var(--accent);
  background: linear-gradient(160deg, #ff9f5f, var(--accent));
}

.btn-accent:hover:not(:disabled) {
  background: linear-gradient(160deg, #f28c48, var(--accent-strong));
}

.btn-tool.active {
  border-color: var(--tool-active-border);
  background: var(--tool-active-bg);
  color: var(--tool-active-ink);
}

.separator {
  width: 1px;
  height: 28px;
  margin: 0 0.15rem;
  background: linear-gradient(transparent, #c8d7ef, transparent);
}

.tool-group {
  display: flex;
  align-items: center;
  gap: 0.35rem;
}

.tool-label {
  font-size: 0.88rem;
  color: var(--muted);
}

.control {
  display: flex;
  align-items: center;
  gap: 0.42rem;
  font-size: 0.86rem;
  color: var(--muted);
}

.control input,
.control textarea {
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 0.38rem 0.48rem;
  font: inherit;
  color: var(--ink);
  background: var(--input-bg);
}

.control input[type="text"],
.control input[type="password"],
.control input[type="number"],
.control textarea {
  min-width: 140px;
}

.control-wide {
  flex: 1;
  min-width: 210px;
}

.control-wide input {
  width: 100%;
}

.control textarea {
  width: 100%;
  resize: vertical;
}

.zoom-control input[type="range"] {
  width: 120px;
}

#zoomValue {
  font-weight: 700;
  color: var(--zoom-color);
  min-width: 46px;
}

.layout {
  display: grid;
  grid-template-columns: 320px minmax(0, 1fr);
  gap: 1rem;
}

.sidebar,
.editor,
.equation {
  padding: 0.92rem;
  animation: rise 0.5s ease-out;
}

.sidebar {
  min-height: 520px;
}

.sidebar-header h2,
.editor-header h2,
.equation-head h2 {
  margin: 0;
  font-family: "Sora", sans-serif;
  font-size: 1.1rem;
}

.sidebar-header p,
.editor-header p,
.equation-head p {
  margin: 0.22rem 0 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.page-list {
  margin: 0.85rem 0 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
  max-height: 72vh;
  overflow: auto;
}

.page-item {
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 0.46rem;
  background: var(--item-bg);
  display: grid;
  grid-template-columns: auto auto 1fr auto;
  gap: 0.46rem;
  align-items: center;
  cursor: pointer;
  transition: border-color 0.2s ease, transform 0.2s ease, box-shadow 0.2s ease;
}

.page-item:hover {
  transform: translateY(-1px);
  box-shadow: 0 10px 20px rgba(19, 58, 112, 0.1);
}

.page-item.dragging {
  opacity: 0.42;
}

.page-item.selected {
  border-color: #9ac7ef;
  background: var(--item-selected-bg);
}

.drag-handle {
  color: #6a7f9f;
  font-size: 1.2rem;
  user-select: none;
}

.thumb {
  width: 86px;
  border: 1px solid #dae5f4;
  border-radius: 8px;
  display: block;
}

.page-meta {
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 0.28rem;
}

.page-name {
  font-size: 0.88rem;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.delete-page {
  border: 1px solid #f8c5bb;
  background: #fff5f3;
  color: var(--danger);
  border-radius: 9px;
  width: 30px;
  height: 30px;
  cursor: pointer;
}

.editor {
  min-height: 650px;
}

.canvas-stage {
  position: relative;
  margin-top: 0.8rem;
  width: 100%;
  min-height: 72vh;
  padding: 0.85rem;
  border: 1px solid var(--canvas-border);
  border-radius: 14px;
  overflow: auto;
  background:
    linear-gradient(45deg, var(--canvas-grid) 25%, transparent 25%),
    linear-gradient(-45deg, var(--canvas-grid) 25%, transparent 25%),
    linear-gradient(45deg, transparent 75%, var(--canvas-grid) 75%),
    linear-gradient(-45deg, transparent 75%, var(--canvas-grid) 75%),
    var(--canvas-bg);
  background-size: 20px 20px;
  background-position: 0 0, 0 10px, 10px -10px, -10px 0;
}

#pdfCanvas,
#overlayCanvas {
  display: block;
  max-width: none;
  transform-origin: top left;
}

#overlayCanvas {
  position: absolute;
  top: 0.85rem;
  left: 0.85rem;
  cursor: crosshair;
}

.text-box-editor {
  position: absolute;
  z-index: 6;
  min-height: 2.6em;
  padding: 0.38rem 0.48rem;
  border: 1px solid var(--editor-border);
  border-radius: 10px;
  background: var(--editor-bg);
  box-shadow: 0 10px 24px rgba(24, 61, 118, 0.2);
  line-height: 1.25;
  resize: both;
  outline: none;
}

.text-box-editor:focus {
  border-color: var(--editor-border-focus);
  box-shadow: 0 0 0 2px rgba(61, 141, 224, 0.2), 0 12px 24px rgba(24, 61, 118, 0.22);
}

.equation {
  margin-top: 1rem;
}

.equation-controls {
  margin-top: 0.7rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  align-items: center;
}

.equation-status {
  margin: 0.6rem 0 0;
  font-size: 0.9rem;
  color: var(--muted);
}

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

@media (max-width: 1080px) {
  .layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    min-height: 320px;
  }

  .page-list {
    max-height: 260px;
  }

  .canvas-stage {
    min-height: 62vh;
  }
}

@media (max-width: 680px) {
  body {
    padding: 0.75rem;
  }

  .topbar {
    flex-direction: column;
    align-items: flex-start;
  }

  .status-pill {
    width: 100%;
  }

  .toolbar {
    position: static;
  }

  .control {
    width: 100%;
    justify-content: space-between;
  }

  .tool-group {
    width: 100%;
  }

  .zoom-control input[type="range"] {
    width: 100%;
    max-width: 160px;
  }

  .canvas-stage {
    min-height: 56vh;
    padding: 0.6rem;
  }

  #overlayCanvas {
    top: 0.6rem;
    left: 0.6rem;
  }
}