:root {
  --bg: #f4f7fb;
  --panel: #ffffff;
  --panel-border: #d9e3f0;
  --ink: #1f2937;
  --ink-soft: #5f6e83;
  --accent: #2455d6;
  --accent-2: #1a8b57;
  --shadow: 0 10px 28px rgba(15, 23, 42, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  color: var(--ink);
  background:
    radial-gradient(circle at 8% 10%, rgba(36, 85, 214, 0.12), transparent 40%),
    radial-gradient(
      circle at 92% 88%,
      rgba(26, 139, 87, 0.12),
      transparent 42%
    ),
    var(--bg);
  font-family: "Avenir Next", "Segoe UI", sans-serif;
}

.gdn-page {
  width: min(1200px, 94vw);
  margin: 22px auto;
}

.gdn-header {
  padding: 8px 6px 16px;
}

.gdn-header h1 {
  margin: 0;
  font-size: clamp(1.6rem, 2.6vw, 2.2rem);
  letter-spacing: 0.01em;
}

.gdn-header p {
  margin: 8px 0 0;
  color: var(--ink-soft);
}

.gdn-main {
  display: grid;
  grid-template-columns: 330px 1fr;
  gap: 18px;
}

.gdn-panel {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 14px;
  box-shadow: var(--shadow);
}

.gdn-controls {
  padding: 16px 16px 20px;
}

.gdn-controls h2 {
  margin: 0 0 12px;
  font-size: 1.08rem;
}

.gdn-field {
  display: grid;
  gap: 7px;
  margin-bottom: 12px;
  font-size: 0.92rem;
}

.gdn-field select,
.gdn-field input[type="number"] {
  width: 100%;
  border: 1px solid #cbd6e5;
  border-radius: 8px;
  padding: 7px 9px;
  font-size: 0.95rem;
  background: #fff;
  color: var(--ink);
}

.gdn-field input[type="range"] {
  width: 100%;
  accent-color: var(--accent);
}

.gdn-field strong {
  font-size: 0.84rem;
  color: var(--ink-soft);
  font-weight: 600;
}

.gdn-inline-checks {
  display: grid;
  gap: 8px;
  margin: 12px 0;
}

.gdn-inline-checks label {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--ink-soft);
}

.gdn-actions {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
  margin-top: 14px;
}

.gdn-actions button {
  border: none;
  border-radius: 9px;
  padding: 8px 6px;
  font-size: 0.9rem;
  cursor: pointer;
  color: #fff;
  background: linear-gradient(120deg, var(--accent), #3c6ae0);
  transition: transform 0.14s ease;
}

.gdn-actions button:hover {
  transform: translateY(-1px);
}

.gdn-visual {
  padding: 14px;
}

#contourCanvas,
#convergenceCanvas {
  width: 100%;
  display: block;
  border: 1px solid #d2ddeb;
  border-radius: 12px;
  background: #fff;
}

#contourCanvas {
  height: 460px;
}

#convergenceCanvas {
  margin-top: 10px;
  height: 220px;
}

.gdn-hint {
  margin: 8px 4px 10px;
  color: var(--ink-soft);
  font-size: 0.88rem;
}

.gdn-metrics {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
  margin-bottom: 10px;
}

.gdn-metrics > div {
  border: 1px solid #d9e3f0;
  border-radius: 10px;
  padding: 8px;
  background: #f8fbff;
  font-size: 0.88rem;
  color: var(--ink-soft);
}

.gdn-metrics strong {
  color: var(--ink);
}

.gdn-formulas {
  border: 1px solid #d8e2ee;
  border-radius: 10px;
  padding: 8px;
  margin: 8px 0 12px;
  background: #fbfdff;
}

.gdn-formula {
  min-height: 38px;
  color: #0f172a;
  overflow-x: auto;
}

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

  .gdn-controls {
    order: 2;
  }

  .gdn-visual {
    order: 1;
  }
}

@media (max-width: 640px) {
  .gdn-page {
    width: 96vw;
    margin: 12px auto;
  }

  #contourCanvas {
    height: 360px;
  }

  #convergenceCanvas {
    height: 190px;
  }

  .gdn-actions {
    grid-template-columns: 1fr;
  }

  .gdn-metrics {
    grid-template-columns: 1fr;
  }
}