/* Shared semantic palette. light-dark preserves approved light colors in
   component styles; the used color-scheme also reaches native controls/SVGs. */
:root {
    color-scheme: light dark;
    --bg: light-dark(#f5f7fb, #101827);
    --surface: light-dark(#ffffff, #182335);
    --surface-raised: light-dark(#ffffff, #202e43);
    --surface-soft: light-dark(#f8fafc, #141f30);
    --input-surface: light-dark(#ffffff, #101c2d);
    --text: light-dark(#172033, #e2e9f3);
    --muted: light-dark(#607086, #b3c2d5);
    --text-muted: light-dark(#53657a, #b3c2d5);
    --primary: light-dark(#1d4ed8, #9ac4ff);
    --primary-dark: light-dark(#1e40af, #bedaff);
    --primary-soft: light-dark(#eff6ff, #203654);
    --button-bg: light-dark(#1d4ed8, #244db0);
    --button-hover: light-dark(#1e40af, #2a57c1);
    --on-primary: #f8fafc;
    --border: light-dark(#e2e8f0, #3b4d65);
    --border-color: light-dark(#dbe3ee, #3b4d65);
    --border-strong: light-dark(#8292a8, #8499b3);
    --focus: light-dark(#1d4ed8, #f6cd75);
    --success-bg: light-dark(#ecfdf5, #173a33);
    --success-text: light-dark(#047857, #92dac2);
    --danger-bg: light-dark(#fef2f2, #402c36);
    --danger-text: light-dark(#b91c1c, #ffb4b4);
    --danger-border: light-dark(#fecaca, #a16b79);
    --warning-bg: light-dark(#fff5df, #3a3020);
    --warning-text: light-dark(#a65307, #efc784);
    --education-ink: light-dark(#10233f, #e2e9f3);
    --education-muted: light-dark(#53657d, #b3c2d5);
    --education-blue: light-dark(#1746a2, #9ac4ff);
    --education-blue-dark: light-dark(#10377f, #bedaff);
    --education-sky: light-dark(#eaf2ff, #203654);
    --education-teal: light-dark(#087f78, #8ed9cf);
    --education-teal-soft: light-dark(#e7f8f5, #183934);
    --education-amber: light-dark(#a65307, #efc784);
    --education-amber-soft: var(--warning-bg);
    --education-border: light-dark(#d8e1ed, #3b4d65);
    --education-surface: var(--surface);
    --chart-series: light-dark(#43516a, #d5dfed);
    --chart-secondary: light-dark(#b8d7ff, #547fb2);
    --chart-accent: light-dark(#2563eb, #a6ccff);
}
:root[data-theme="light"] { color-scheme: light; }
:root[data-theme="dark"] { color-scheme: dark; }

/* Filled actions have their own ink/background pair; links use primary. */
.education-method { background: light-dark(#10233f, #141f30); }
.calculator-hero p { color: var(--text-muted); }
:is(input:not([type="checkbox"]):not([type="radio"]):not([type="submit"]), select, textarea) {
    background-color: var(--input-surface);
    color: var(--text);
    border-color: var(--border-strong);
}
input::placeholder, textarea::placeholder { color: var(--muted); opacity: 1; }
input[type="checkbox"], input[type="radio"] { accent-color: var(--button-bg); }
a:focus-visible, button:focus-visible, summary:focus-visible,
input:focus-visible, select:focus-visible, textarea:focus-visible,
html [name]:focus-visible,
[tabindex]:focus-visible {
    outline: 3px solid var(--focus);
    outline-offset: 3px;
    box-shadow: 0 0 0 5px var(--surface);
}
.education-lesson a:focus-visible,
.education-lesson summary:focus-visible,
.education-lesson [tabindex]:focus-visible,
.menu-panel a:focus-visible,
.theme-control select:focus-visible { outline-color: var(--focus); }

/* Navigation: four stable areas, one clear starting point per learning task. */
.header-actions { display: flex; align-items: center; gap: 12px; flex-shrink: 0; }
.theme-control { display: flex; align-items: center; gap: 6px; font-size: 0.8rem; color: var(--text-muted); }
.theme-control[hidden] { display: none; }
.theme-control select {
    width: auto; min-height: 44px; margin: 0; padding: 8px 6px;
    border-radius: var(--radius-sm); border: 1px solid var(--border-color);
    font: inherit; cursor: pointer;
}
.menu-panel {
    /* Immediate disclosure also makes the first mobile focus deterministic. */
    transition: none;
    display: none; visibility: visible; opacity: 1; transform: none;
    width: min(1180px, calc(100vw - 40px));
    grid-template-columns: minmax(370px, 2fr) minmax(150px, 0.9fr) minmax(200px, 1.2fr) minmax(170px, 1fr) !important;
    padding: 24px; border-radius: var(--radius-md);
    background: var(--surface-raised); box-shadow: 0 8px 24px rgba(10, 18, 30, 0.12);
}
.menu-accordion { padding-inline: 18px; }
.menu-dropdown.is-open .menu-panel { display: grid; }
.menu-desktop-heading { color: var(--text-muted); font-weight: 700; letter-spacing: 0.06em; }
.menu-overview-link {
    padding: 10px; margin: 0 0 4px; gap: 5px; font-size: 0.92rem;
    line-height: 1.4; background: var(--primary-soft); color: var(--primary-dark);
}
.menu-overview-link small, .menu-contest-link small {
    display: block; font-size: 0.78rem; font-weight: 400; line-height: 1.5; color: var(--text-muted);
}
.menu-category-link, .menu-link-list a { font-weight: 500; color: var(--text); }
.menu-category-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    grid-auto-rows: 1fr; gap: 4px 8px;
}
.menu-category-link {
    display: flex; align-items: center; justify-content: space-between; gap: 6px;
    min-width: 0; min-height: 38px; padding: 2px 8px; font-size: 0.84rem; line-height: 1.2;
    border: 1px solid var(--border); border-radius: var(--radius-sm);
}
.menu-category-link > span:first-child { min-width: 0; overflow-wrap: break-word; }
.menu-category-arrow { flex: 0 0 auto; color: var(--text-muted); }
.menu-panel .menu-category-link:is(:hover, :focus-visible) {
    background: var(--surface-soft); border-color: var(--border-strong); color: var(--primary-dark);
    text-decoration: none;
}
.menu-category-link:is(:hover, :focus-visible) .menu-category-arrow { color: currentColor; }
.menu-link-list .menu-contest-link { display: grid; gap: 5px; margin-top: 5px; }
.menu-contest-link > span { color: var(--primary); font-weight: 700; }
.menu-panel a:hover { text-decoration: underline; text-underline-offset: 3px; }
.menu-panel a:active { background: var(--primary-soft); }
.menu-science-links a { border-radius: 4px; font-weight: 500; background: transparent; padding: 3px 0; }
.menu-science-links { gap: 10px; }
@media (min-width: 781px) and (max-width: 980px) {
    .menu-panel { grid-template-columns: 1.5fr 1fr !important; gap: 24px 0; }
    .menu-accordion:nth-child(3) { padding-left: 0; border-left: 0; }
}
@media (max-width: 780px) {
    .header-actions { gap: 8px; }
    .menu-panel { width: auto; grid-template-columns: 1fr !important; gap: 0; padding: 8px 12px; }
    .menu-accordion, .menu-accordion:first-child, .menu-accordion:last-child {
        overflow: visible; border: 0; border-bottom: 1px solid var(--border); border-radius: 0;
        background: transparent;
    }
    .menu-accordion:last-child { border-bottom: 0; }
    .menu-section-toggle { padding-inline: 4px; }
    .menu-section-content { padding: 0 0 12px; }
    .menu-section-content[hidden] { display: none; }
    .menu-overview-link { min-height: 44px; }
    .menu-category-link { min-height: 44px; padding-block: 5px; }
}
@media (max-width: 520px) {
    .brand-name { white-space: normal; max-width: 96px; line-height: 1.25; }
    .brand { gap: 6px; }
    .brand-logo { width: 30px; height: 30px; }
    .theme-control { display: grid; gap: 0; position: relative; }
    .theme-control > span { position: absolute; left: 8px; top: 2px; font-size: 0.6rem; pointer-events: none; }
    .theme-control select { padding: 14px 3px 2px; max-width: 82px; font-size: 0.75rem; }
    .header-content { gap: 6px; }
    .menu-button { min-height: 44px; padding-inline: 8px; }
}
/* Below 600px, long category names need the full row. At 768px both
   columns comfortably fit; keep the existing accordion behavior. */
@media (max-width: 599px) {
    .menu-category-grid { grid-template-columns: 1fr; }
}
@media (prefers-reduced-motion: reduce) {
    html { scroll-behavior: auto; }
}