:root {
  --app-bg: #f7f7f4;
  --surface: #ffffff;
  --surface-soft: #f3f4f2;
  --surface-strong: #e9ece7;
  --text: #202124;
  --muted: #667085;
  --border: #d9ded8;
  --border-strong: #c4cbc2;
  --blue: #2d70b3;
  --blue-dark: #255d95;
  --red: #c74440;
  --green: #388c46;
  --warning: #9a6700;
  --shadow: 0 18px 45px rgba(31, 41, 55, 0.08);
}

* {
  box-sizing: border-box;
}

html {
  scroll-padding-top: 98px;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background:
    linear-gradient(rgba(217, 222, 216, 0.48) 1px, transparent 1px),
    linear-gradient(90deg, rgba(217, 222, 216, 0.48) 1px, transparent 1px),
    var(--app-bg);
  background-size: 28px 28px;
  color: var(--text);
}

button,
input {
  font: inherit;
}

button {
  min-height: 40px;
  border: 1px solid var(--blue-dark);
  border-radius: 6px;
  background: var(--blue);
  color: #ffffff;
  font-size: 0.9rem;
  font-weight: 700;
  cursor: pointer;
  transition: background 0.16s ease, border-color 0.16s ease, box-shadow 0.16s ease, transform 0.16s ease;
}

button:hover {
  background: var(--blue-dark);
  box-shadow: 0 10px 22px rgba(45, 112, 179, 0.2);
  transform: translateY(-1px);
}

button:active {
  transform: translateY(0);
}

h1,
h2,
h3,
p,
dl,
dd {
  margin: 0;
}

.app-header {
  min-height: 82px;
  padding: 14px 22px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  background: rgba(255, 255, 255, 0.92);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(16px);
  position: sticky;
  top: 0;
  z-index: 10;
}

.eyebrow {
  margin-bottom: 3px;
  color: var(--green);
  font-size: 0.73rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1 {
  font-size: 1.85rem;
  line-height: 1.05;
  font-weight: 700;
}

.subtitle {
  margin-top: 5px;
  color: var(--muted);
  font-size: 0.9rem;
  line-height: 1.35;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.header-actions button {
  width: auto;
  min-width: 104px;
  padding: 0 14px;
}

.secondary-button {
  background: var(--surface);
  color: var(--text);
  border-color: var(--border-strong);
}

.secondary-button:hover {
  background: var(--surface-strong);
  border-color: var(--border-strong);
  box-shadow: none;
}

.toggle {
  min-height: 40px;
  padding: 0 12px;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  border: 1px solid var(--border-strong);
  border-radius: 6px;
  background: var(--surface);
  color: var(--text);
  font-size: 0.86rem;
  font-weight: 700;
  white-space: nowrap;
}

.toggle input {
  width: 16px;
  height: 16px;
  accent-color: var(--blue);
}

.workspace {
  display: grid;
  grid-template-columns: minmax(330px, 410px) minmax(0, 1fr);
  gap: 18px;
  width: min(1580px, 100%);
  margin: 0 auto;
  padding: 18px;
}

.control-panel {
  align-self: start;
  display: grid;
  gap: 14px;
  position: sticky;
  top: 100px;
}

.control-section,
.graph-card,
.status-message {
  background: rgba(255, 255, 255, 0.96);
  border: 1px solid var(--border);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.control-section {
  padding: 15px;
}

.section-heading {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 11px;
  align-items: start;
  padding-bottom: 13px;
  border-bottom: 1px solid var(--border);
}

.section-index {
  width: 28px;
  height: 28px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: var(--surface-soft);
  color: var(--green);
  border: 1px solid var(--border);
  font-size: 0.86rem;
  font-weight: 700;
}

h2 {
  font-size: 1rem;
  line-height: 1.2;
}

.section-heading p {
  margin-top: 3px;
  color: var(--muted);
  font-size: 0.82rem;
  line-height: 1.4;
}

.preset-grid,
.input-grid,
.metric-row {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 9px;
  margin-top: 13px;
}

.preset-button {
  width: 100%;
  background: var(--surface);
  border-color: var(--border-strong);
  color: var(--text);
}

.preset-button:hover,
.preset-button.is-active {
  background: #eef5fb;
  border-color: var(--blue);
  color: var(--blue-dark);
  box-shadow: none;
}

.expression-list {
  display: grid;
  gap: 8px;
  margin-top: 13px;
}

.expression-row {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 10px;
  align-items: start;
  padding: 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--surface-soft);
}

.expression-row i {
  width: 22px;
  height: 3px;
  margin-top: 9px;
  border-radius: 999px;
}

.expression-row strong,
.expression-row span {
  display: block;
}

.expression-row strong {
  font-size: 0.82rem;
}

.expression-row span {
  margin-top: 4px;
  color: var(--muted);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.72rem;
  line-height: 1.35;
}

.mini-heading {
  margin-top: 14px;
  padding-top: 13px;
  border-top: 1px solid var(--border);
}

.mini-heading h3 {
  font-size: 0.88rem;
}

.mini-heading p {
  margin-top: 3px;
  color: var(--muted);
  font-size: 0.78rem;
  line-height: 1.35;
}

label {
  min-width: 0;
  display: grid;
  gap: 6px;
  color: var(--text);
  font-size: 0.78rem;
  font-weight: 600;
}

label span {
  color: var(--muted);
  font-size: 0.7rem;
  font-weight: 500;
  margin-left: 3px;
}

input {
  width: 100%;
  min-height: 38px;
  padding: 8px 10px;
  border: 1px solid var(--border-strong);
  border-radius: 6px;
  background: var(--surface);
  color: var(--text);
  outline: none;
  transition: border-color 0.16s ease, box-shadow 0.16s ease;
}

input:focus {
  border-color: var(--blue);
  box-shadow: 0 0 0 3px rgba(45, 112, 179, 0.14);
}

input.is-invalid {
  border-color: var(--red);
  box-shadow: 0 0 0 3px rgba(199, 68, 64, 0.1);
}

input[type="range"] {
  min-height: 24px;
  padding: 0;
  border: 0;
  accent-color: var(--blue);
  background: transparent;
  box-shadow: none;
}

.slider-stack {
  display: grid;
  gap: 10px;
  margin-top: 13px;
  padding: 11px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--surface-soft);
}

.slider-field {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 8px;
}

.slider-field input {
  grid-column: 1 / -1;
}

.control-section > button:not(.preset-button) {
  width: 100%;
  margin-top: 13px;
}

.metric {
  min-height: 58px;
  padding: 9px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--surface-soft);
}

.metric span {
  display: block;
  color: var(--muted);
  font-size: 0.68rem;
  font-weight: 700;
  text-transform: uppercase;
}

.metric strong {
  display: block;
  margin-top: 5px;
  color: var(--text);
  font-size: 0.98rem;
}

.reference-section {
  display: block;
}

.equation-list {
  display: grid;
  gap: 8px;
  margin-top: 13px;
}

.equation-list div {
  padding: 9px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--surface-soft);
}

.equation-list dt {
  color: var(--muted);
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
}

.equation-list dd {
  margin-top: 4px;
  color: var(--text);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.82rem;
}

.graph-panel {
  min-width: 0;
}

.status-message {
  min-height: 42px;
  margin-bottom: 14px;
  padding: 11px 13px;
  color: var(--muted);
  font-size: 0.88rem;
  font-weight: 600;
}

.status-message.is-warning {
  color: var(--warning);
  border-color: rgba(154, 103, 0, 0.35);
  background: #fff8e6;
}

.status-message.is-error {
  color: var(--red);
  border-color: rgba(199, 68, 64, 0.35);
  background: #fff1f0;
}

.analysis-panel {
  display: grid;
  grid-template-columns: minmax(260px, 0.8fr) minmax(360px, 1fr);
  gap: 14px;
  margin-bottom: 14px;
}

.animation-controls,
.comparison-table-wrap {
  background: rgba(255, 255, 255, 0.96);
  border: 1px solid var(--border);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.animation-controls {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 12px;
  align-items: center;
  padding: 12px;
}

.animation-controls button {
  min-width: 74px;
}

.animation-controls label {
  display: grid;
  grid-template-columns: auto auto;
  align-items: center;
}

.animation-controls label span {
  justify-self: end;
}

.animation-controls input {
  grid-column: 1 / -1;
}

.comparison-table-wrap {
  overflow-x: auto;
}

.comparison-table {
  width: 100%;
  min-width: 520px;
  border-collapse: collapse;
  font-size: 0.82rem;
}

.comparison-table th,
.comparison-table td {
  padding: 10px;
  border-bottom: 1px solid var(--border);
  text-align: left;
  white-space: nowrap;
}

.comparison-table th {
  color: var(--muted);
  font-size: 0.7rem;
  text-transform: uppercase;
}

.comparison-table tbody tr:last-child td {
  border-bottom: 0;
}

.graph-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.graph-card {
  min-width: 0;
  min-height: 330px;
  padding: 14px;
  display: grid;
  grid-template-rows: auto minmax(260px, 1fr);
  scroll-margin-top: 98px;
}

.graph-card-wide {
  grid-column: 1 / -1;
  min-height: 430px;
  grid-template-rows: auto minmax(360px, 1fr);
}

.graph-title {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: center;
  padding-bottom: 11px;
  border-bottom: 1px solid var(--border);
}

h3 {
  font-size: 0.96rem;
  line-height: 1.2;
}

.graph-title span {
  display: block;
  margin-top: 3px;
  color: var(--muted);
  font-size: 0.8rem;
  font-weight: 600;
}

.chart-download {
  min-width: 56px;
  min-height: 32px;
  padding: 0 10px;
  position: relative;
  z-index: 1;
  background: var(--surface);
  border-color: var(--border-strong);
  color: var(--text);
  font-size: 0.76rem;
}

.chart-download:hover {
  background: var(--surface-strong);
  border-color: var(--border-strong);
  box-shadow: none;
}

canvas {
  width: 100% !important;
  height: 100% !important;
  min-height: 0;
}

@media (max-width: 1100px) {
  .workspace {
    grid-template-columns: 1fr;
  }

  .control-panel {
    position: static;
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .reference-section {
    grid-column: 1 / -1;
  }

  .equation-list {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .analysis-panel {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 760px) {
  .app-header {
    position: static;
    align-items: flex-start;
    flex-direction: column;
  }

  .header-actions {
    width: 100%;
    justify-content: stretch;
  }

  .header-actions button,
  .toggle {
    flex: 1 1 130px;
    justify-content: center;
  }

  .workspace {
    padding: 12px;
  }

  .control-panel,
  .graph-grid,
  .equation-list {
    grid-template-columns: 1fr;
  }

  .reference-section {
    grid-column: auto;
  }

  .graph-card,
  .graph-card-wide {
    grid-column: auto;
    min-height: 320px;
    grid-template-rows: auto minmax(250px, 1fr);
  }
}

@media (max-width: 430px) {
  h1 {
    font-size: 1.55rem;
  }

  .preset-grid,
  .input-grid,
  .metric-row {
    grid-template-columns: 1fr;
  }
}