:root {
  --bg: #F5F5F5;
  --fg: #454545;
  --body-fg: rgb(55, 55, 55);
  --muted: #6b6b6b;
  --accent: #657abe;
  --accent-hover: #4e62a3;
  --accent-interactive: #31BEF2;
  --accent-interactive-hover: #1fa3d4;
  --accent-light: #EEE;
  --border: #DDD;
  --input-bg: #f5f5f5;
  --input-border: #ccc;
  --warn-bg: #fff4e8;
  --warn-border: #e8c08c;
  --card: #FFF;
  --radius: 4px;
  --shadow: 0 2px 2px #CCC;
  --inset-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.05);
  --gap: 1rem;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--fg);
  background: var(--bg);
}

.container { max-width: 980px; margin: 0 auto; padding: 0 1.2rem; }

.site-header { background: var(--accent); color: #fff; padding: 1.5rem 0; }
.site-title {
  margin: 0;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 24px;
  font-weight: 600;
  color: #fff;
}
.site-tagline {
  margin: 0.3rem 0 0;
  color: #EEE;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 0.95rem;
}

main.container { padding-top: 1.5rem; padding-bottom: 2rem; }

.site-footer { border-top: 1px solid var(--border); margin-top: 2rem; background: var(--card); }
.site-footer p { margin: 1rem 0; color: var(--muted); font-size: 0.9rem; }

.muted { color: var(--muted); }
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0;
}

.calc-layout { display: grid; gap: var(--gap); }

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow), var(--inset-shadow);
  padding: 1.2rem 1.3rem;
}
form.card { background: var(--input-bg); }

.logo-card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1rem 1.1rem 0.9rem;
  margin: 0 0 1rem;
  background: var(--card);
}
.logo-card h3 {
  margin: 0 0 0.25rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 18px;
  color: var(--accent);
}
.logo-card .section-desc { margin: 0 0 0.6rem; }
.logo-form { display: flex; gap: 0.6rem; align-items: center; margin: 0.6rem 0; flex-wrap: wrap; }
.logo-status { min-height: 2rem; }
.logo-preview { display: flex; align-items: center; gap: 0.8rem; margin: 0.4rem 0; }
.logo-preview img { max-height: 3.5rem; border: 1px solid var(--border); border-radius: 4px; background: #fff; padding: 2px; }
.logo-preview figcaption { font-size: 0.85rem; color: var(--muted); }

.section {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1rem 1.1rem 0.8rem;
  margin: 0 0 1rem;
  background: var(--card);
}
.section:last-of-type { margin-bottom: 0.4rem; }
.section-title {
  font-weight: 600;
  color: var(--accent);
  padding: 0 0.4rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 18px;
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
}
.section-title-text { line-height: 1.2; }

.tooltip {
  position: relative;
  display: inline-flex;
  align-items: center;
}
.tooltip-trigger {
  appearance: none;
  border: 1px solid var(--accent);
  background: var(--card);
  color: var(--accent);
  width: 1.2rem;
  height: 1.2rem;
  border-radius: 50%;
  font-family: Georgia, "Times New Roman", serif;
  font-style: italic;
  font-weight: 700;
  font-size: 0.85rem;
  line-height: 1;
  padding: 0;
  cursor: help;
  transition: background-color 0.15s linear, color 0.15s linear;
}
.tooltip-trigger:hover,
.tooltip-trigger:focus {
  background: var(--accent);
  color: #fff;
  outline: none;
}
.tooltip-trigger:focus-visible {
  outline: 2px solid var(--accent-interactive);
  outline-offset: 2px;
}
.tooltip-content {
  position: absolute;
  left: 50%;
  top: calc(100% + 0.5rem);
  transform: translateX(-50%);
  min-width: 14rem;
  max-width: min(22rem, 90vw);
  padding: 0.6rem 0.75rem;
  background: #2b2b2b;
  color: #fff;
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
  font-size: 0.85rem;
  font-weight: 400;
  line-height: 1.45;
  text-align: left;
  border-radius: 4px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.18);
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transition: opacity 0.15s linear, visibility 0.15s linear;
  z-index: 10;
  white-space: normal;
}
.tooltip-content::before {
  content: "";
  position: absolute;
  left: 50%;
  bottom: 100%;
  transform: translateX(-50%);
  border: 6px solid transparent;
  border-bottom-color: #2b2b2b;
}
.tooltip-trigger:hover + .tooltip-content,
.tooltip-trigger:focus + .tooltip-content,
.tooltip:hover .tooltip-content,
.tooltip:focus-within .tooltip-content {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
}
@media (max-width: 600px) {
  .tooltip-content {
    left: 0;
    transform: none;
    min-width: 12rem;
    max-width: calc(100vw - 3rem);
  }
  .tooltip-content::before {
    left: 0.6rem;
    transform: none;
  }
}
.section-desc {
  margin: 0 0 0.6rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 14px;
  color: var(--body-fg);
}
.section-fields { display: grid; gap: 0.9rem; grid-template-columns: 1fr; }
@media (min-width: 720px) {
  .section-fields { grid-template-columns: repeat(2, 1fr); }
}

.field { display: flex; flex-direction: column; gap: 0.3rem; }
.field-label {
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-weight: 500;
  color: var(--fg);
}
.field-unit { font-weight: 400; color: var(--muted); font-size: 0.9em; }
.req { color: #b42318; margin-left: 2px; }
.field-help {
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 13px;
  color: var(--muted);
}

.field input[type=text], .field input[type=number], .field select {
  padding: 0.4rem 0.55rem;
  border: 1px solid var(--input-border);
  border-radius: 3px;
  font: inherit;
  background: #fff;
  color: var(--fg);
  box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075);
  transition: border-color 0.2s linear, box-shadow 0.2s linear;
}
.field input[type=text]:focus, .field input[type=number]:focus, .field select:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
  border-color: var(--accent);
}

.radio-group {
  border: none; padding: 0; margin: 0;
  display: flex; flex-direction: column; gap: 0.25rem;
}
.radio-group legend { padding: 0; font-weight: 500; }
.radio-option { display: flex; gap: 0.45rem; align-items: center; font-weight: 400; }
.radio-option input[type=radio] { accent-color: var(--accent); }
.checkbox-label { display: flex; gap: 0.45rem; align-items: center; font-weight: 500; }
.checkbox-label input { accent-color: var(--accent); }

.form-actions {
  display: flex; gap: 0.7rem; flex-wrap: wrap;
  margin-top: 1rem; padding-top: 1rem;
  border-top: 1px dashed var(--border);
}

.btn {
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 15px;
  cursor: pointer;
  border-radius: 4px;
  border: 1px solid transparent;
  padding: 0.55rem 1.1rem;
  font-weight: 500;
  transition: background-color 0.15s linear, color 0.15s linear;
}
.btn-primary {
  background: var(--accent-interactive);
  color: #fff;
  border-color: var(--accent-interactive);
}
.btn-primary:hover {
  background: var(--accent-interactive-hover);
  border-color: var(--accent-interactive-hover);
}
.btn-secondary {
  background: var(--card);
  color: var(--accent);
  border-color: var(--border);
}
.btn-secondary:hover { background: var(--accent-light); }
.btn-link {
  background: transparent;
  border: none;
  color: var(--accent-interactive);
  padding: 0.3rem 0.1rem;
}
.btn-link:hover {
  color: var(--accent-interactive-hover);
  text-decoration: underline;
}

.alert {
  padding: 0.8rem 1rem;
  border-radius: 4px;
  border: 1px solid transparent;
  margin: 0 0 1rem;
}
.alert-warn { background: var(--warn-bg); border-color: var(--warn-border); color: #794a11; }
.alert-warn h3 {
  margin: 0 0 0.3rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 16px;
}
.alert-warn ul { margin: 0; padding-left: 1.2rem; }

.results { min-height: 1rem; }
.results-card { margin-top: 1rem; }
.results-header {
  display: flex; justify-content: space-between; align-items: center;
  gap: 1rem; flex-wrap: wrap; margin-bottom: 0.8rem;
}
.results-header h3 {
  margin: 0;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 20px;
  color: var(--accent);
}
.report-form { margin: 0; }

.results-grid { display: grid; gap: 1rem; grid-template-columns: 1fr; }
@media (min-width: 820px) { .results-grid { grid-template-columns: repeat(2, 1fr); } }

.results-table {
  width: 100%; border-collapse: collapse; font-size: 0.93rem; margin: 0.4rem 0 0.8rem;
}
.results-table caption {
  text-align: left;
  font-weight: 600;
  color: var(--accent);
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 16px;
  padding: 0.25rem 0 0.35rem;
}
.results-table th, .results-table td {
  padding: 0.35rem 0.55rem; border-bottom: 1px solid var(--border);
  text-align: left; vertical-align: top;
}
.results-table th[scope=row] { font-weight: 500; }
.results-table td:nth-child(2) { text-align: right; font-variant-numeric: tabular-nums; }

.notes { margin-top: 1rem; padding: 0.8rem 1rem; border-radius: 4px; }
.notes h4 {
  margin: 0 0 0.4rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 16px;
}
.notes ul { margin: 0; padding-left: 1.2rem; }
.notes-warn { background: var(--warn-bg); border: 1px solid var(--warn-border); }
.notes-plain { background: var(--accent-light); border: 1px solid var(--border); }

.admix-block {
  margin-top: 1rem;
  padding: 0.9rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  background: var(--card);
}
.admix-block h4 {
  margin: 0 0 0.25rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 16px;
  color: var(--accent);
}
.admix-block > p.muted { margin: 0 0 0.7rem; }
.admix-card {
  padding: 0.6rem 0.8rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--accent-light);
  margin: 0.6rem 0 0;
}
.admix-card h5 {
  margin: 0 0 0.35rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 15px;
  color: var(--accent);
}
.admix-card p { margin: 0.25rem 0; }
.admix-card ul { margin: 0.35rem 0 0; padding-left: 1.2rem; }
.admix-card li { margin: 0.15rem 0; }

/* --------------------------------------------------------------- intro */
.intro {
  margin: 0 0 1rem;
}
.intro-heading {
  margin: 0 0 0.6rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 20px;
  font-weight: 600;
  color: var(--accent);
}
.intro p {
  margin: 0 0 0.6rem;
  color: var(--body-fg);
}
.intro p:last-child { margin-bottom: 0; }

/* ----------------------------------------------------- sample calculation */
.sample-calc {
  margin: 1.2rem 0 0.4rem;
  padding: 0;
  overflow: hidden;
}
.sample-calc-summary {
  list-style: none;
  cursor: pointer;
  padding: 0.9rem 1.2rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-weight: 600;
  font-size: 17px;
  color: var(--accent);
  display: flex;
  align-items: center;
  gap: 0.55rem;
  user-select: none;
}
.sample-calc-summary::-webkit-details-marker { display: none; }
.sample-calc-summary::before {
  content: "\25B6";
  font-size: 0.75em;
  color: var(--accent);
  transition: transform 0.15s linear;
  display: inline-block;
}
.sample-calc[open] > .sample-calc-summary::before {
  transform: rotate(90deg);
}
.sample-calc-summary:hover { color: var(--accent-hover); }
.sample-calc-summary:focus-visible {
  outline: 2px solid var(--accent-interactive);
  outline-offset: -2px;
}
.sample-calc-body {
  padding: 0 1.3rem 1.2rem;
  border-top: 1px solid var(--border);
  padding-top: 1rem;
}
.sample-calc-body h3 {
  margin: 1.1rem 0 0.35rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 15px;
  color: var(--accent);
}
.sample-calc-body h3:first-of-type { margin-top: 0.6rem; }
.sample-calc-body p { margin: 0.35rem 0; }
.sample-calc-body ul { margin: 0.35rem 0 0.6rem; padding-left: 1.3rem; }
.sample-calc-body li { margin: 0.1rem 0; }
.sample-eq {
  background: var(--accent-light);
  border-left: 3px solid var(--accent);
  padding: 0.5rem 0.75rem;
  margin: 0.4rem 0 0.6rem;
  font-family: "Courier New", Courier, monospace;
  font-size: 0.92rem;
}
.sample-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
  margin: 0.5rem 0 0.6rem;
}
.sample-table th,
.sample-table td {
  padding: 0.3rem 0.55rem;
  border-bottom: 1px solid var(--border);
  text-align: left;
}
.sample-table thead th {
  background: var(--accent-light);
  color: var(--fg);
  font-weight: 600;
}
.sample-table td:not(:first-child) { font-variant-numeric: tabular-nums; }
.sample-table-summary td:nth-child(2) {
  text-align: right;
  font-variant-numeric: tabular-nums;
}

.sample-calc.faq .sample-calc-body h3 {
  margin-top: 1.4rem;
  font-size: 1rem;
}
.sample-calc.faq .sample-calc-body h3:first-of-type { margin-top: 0.4rem; }
.sample-calc.faq .sample-calc-body p { margin: 0.35rem 0 0.1rem; }

/* ----------------------------------------------- dynamic input tables */
.dynamic-table-wrap { overflow-x: auto; }
.layer-table, .surcharge-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
  margin: 0.4rem 0 0.6rem;
}
.layer-table th, .surcharge-table th,
.layer-table td, .surcharge-table td {
  padding: 0.3rem 0.4rem;
  border-bottom: 1px solid var(--border);
  vertical-align: middle;
  text-align: left;
}
.layer-table thead th, .surcharge-table thead th {
  background: var(--accent-light);
  color: var(--fg);
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 13px;
  font-weight: 600;
  white-space: nowrap;
}
.layer-table input[type=text],
.layer-table input[type=number],
.layer-table select,
.surcharge-table input[type=text],
.surcharge-table input[type=number],
.surcharge-table select {
  width: 100%;
  min-width: 5rem;
  padding: 0.3rem 0.4rem;
  border: 1px solid var(--input-border);
  border-radius: 3px;
  font: inherit;
  background: #fff;
  color: var(--fg);
  box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075);
}
.layer-table input:focus,
.layer-table select:focus,
.surcharge-table input:focus,
.surcharge-table select:focus {
  outline: 2px solid var(--accent);
  outline-offset: 1px;
  border-color: var(--accent);
}
.row-actions { display: flex; gap: 0.4rem; flex-wrap: nowrap; }
.row-actions .btn-link { padding: 0.2rem 0.3rem; font-size: 0.85rem; }
.table-actions {
  display: flex; gap: 0.5rem; flex-wrap: wrap; align-items: center;
  margin-top: 0.5rem;
}
.table-actions .btn { padding: 0.4rem 0.85rem; font-size: 0.92rem; }

/* --------------------------------------------------- plots & diagrams */
.plot-grid {
  display: grid;
  gap: 1rem;
  grid-template-columns: 1fr;
  margin: 0.6rem 0;
}
@media (min-width: 820px) {
  .plot-grid { grid-template-columns: repeat(2, 1fr); }
}
.plot-card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card);
  padding: 0.5rem 0.6rem 0.4rem;
}
.plot-card h4 {
  margin: 0 0 0.3rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 14px;
  color: var(--accent);
}
.plot-card svg, .plot-card img { width: 100%; height: auto; display: block; }

.diagram {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--card);
  padding: 0.7rem 0.9rem 0.6rem;
  margin: 0.6rem 0;
}
.diagram h4 {
  margin: 0 0 0.4rem;
  font-family: Arial, "Helvetica Neue", Helvetica, sans-serif;
  font-size: 16px;
  color: var(--accent);
}
.diagram svg, .diagram img { width: 100%; height: auto; display: block; }

.results-tables { display: grid; gap: 1rem; grid-template-columns: 1fr; }
@media (min-width: 820px) { .results-tables { grid-template-columns: repeat(2, 1fr); } }

.results-table th:not(:first-child),
.results-table td:not(:first-child) {
  text-align: right;
  font-variant-numeric: tabular-nums;
}