:root {
  --bg: #f4f5ef;
  --panel: #ffffff;
  --ink: #14222d;
  --muted: #5f6b74;
  --line: #d2d8dd;
  --accent: #0d7a8d;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  height: 100%;
}

body {
  font-family: "IBM Plex Sans", "Segoe UI", Tahoma, sans-serif;
  background: radial-gradient(circle at top right, #e7ebe0, var(--bg) 55%);
  color: var(--ink);
}

.app {
  display: flex;
  flex-direction: column;
  min-height: 100%;
  gap: 0.5rem;
}

.controls {
  padding: 0.72rem 0.9rem 0.1rem;
  background: linear-gradient(180deg, #ffffff, #f9fafb);
  border-bottom: 1px solid var(--line);
}

.controls h1 {
  margin: 0 0 0.6rem;
  font-size: 1.1rem;
  letter-spacing: 0.02em;
}

.row {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 0.35rem;
}

.actions {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  margin-left: auto;
}

input[type="range"] {
  width: min(420px, 72vw);
}

input[type="color"] {
  width: 2.1rem;
  height: 1.8rem;
  padding: 0;
  border: 1px solid #b8c2c9;
  border-radius: 5px;
  background: #ffffff;
  cursor: pointer;
}

select {
  border: 1px solid #b8c2c9;
  border-radius: 6px;
  background: #ffffff;
  color: var(--ink);
  font-size: 0.9rem;
  padding: 0.3rem 0.45rem;
}

.check {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.95rem;
}

.slider-toggle {
  padding: 0.24rem 0.58rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.9);
}

.toggle-groups {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 0.5rem;
  margin-bottom: 0.4rem;
}

.toggle-panel {
  padding: 0.52rem 0.62rem 0.56rem;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.96), rgba(245, 248, 250, 0.92));
  box-shadow: 0 1px 0 rgba(20, 34, 45, 0.02);
}

.panel-title {
  margin: 0 0 0.32rem;
  font-size: 0.74rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
}

.toggle-panel .check {
  display: flex;
  margin-bottom: 0.18rem;
  font-size: 0.86rem;
}

.toggle-panel .check:last-of-type {
  margin-bottom: 0;
}

button {
  border: 1px solid #b8c2c9;
  background: white;
  color: var(--ink);
  border-radius: 6px;
  padding: 0.35rem 0.65rem;
  font-size: 0.9rem;
  cursor: pointer;
}

button:hover {
  background: #f2f6f8;
}

.hint {
  margin: 0 0 0.5rem;
  color: var(--muted);
  font-size: 0.9rem;
}

@media (max-width: 720px) {
  .actions {
    width: 100%;
    margin-left: 0;
  }
}

.canvas-wrap {
  flex: 1;
  min-height: 420px;
  padding: 0.4rem;
  position: relative;
}

#diagram {
  width: 100%;
  height: 100%;
  display: block;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: white;
  touch-action: none;
}

.formula-badge {
  position: absolute;
  top: 0.7rem;
  right: 0.7rem;
  display: inline-flex;
  align-items: center;
  padding: 0.2rem 0.38rem;
  border: 1px solid rgba(210, 216, 221, 0.9);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.9);
  box-shadow: 0 8px 18px rgba(20, 34, 45, 0.08);
  color: var(--ink);
  font-size: 0.64rem;
  line-height: 1;
  pointer-events: none;
  backdrop-filter: blur(4px);
  z-index: 2;
}

.formula-badge math {
  font-size: 0.82rem;
  line-height: 1;
}

.formula-badge math mi,
.formula-badge math mn,
.formula-badge math mo {
  color: var(--ink);
}