/* Standalone styles for the Photoelectric Effect lesson. These selectors are
   deliberately scoped to this module and do not modify the main website CSS. */
:root {
  color-scheme: dark;
  --bg: #0b1220;
  --panel: #111c2e;
  --panel-soft: #16243a;
  --line: rgba(185, 205, 230, .17);
  --text: #edf4ff;
  --muted: #aabbd1;
  --accent: #77c8ff;
  --gold: #f5b942;
  --teal: #69d5c2;
  --violet: #b8a4ff;
  --good: #7ee0b2;
  --bad: #ffad9e;
  --radius: 18px;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}
* { box-sizing: border-box; }
body { margin: 0; background: radial-gradient(ellipse at 15% 0%, #182a43 0, var(--bg) 48%); color: var(--text); line-height: 1.6; }
button, input, select { font: inherit; }
button, select, input[type="range"] { accent-color: var(--accent); }
button { cursor: pointer; }
button:focus-visible, input:focus-visible, select:focus-visible, a:focus-visible { outline: 3px solid var(--gold); outline-offset: 3px; }
.module-header { min-height: 64px; padding: 14px clamp(16px, 4vw, 48px); border-bottom: 1px solid var(--line); display: flex; align-items: center; justify-content: space-between; gap: 16px; }
.site-label { color: var(--text); text-decoration: none; font-weight: 750; letter-spacing: .01em; }
.site-label span { color: var(--muted); font-weight: 500; }
.back-link { color: var(--accent); text-decoration: none; font-size: .92rem; white-space: nowrap; }
.page-shell { width: min(1180px, calc(100% - 32px)); margin: 0 auto; padding: 28px 0 40px; }
.intro-panel { padding: clamp(22px, 4vw, 40px); border: 1px solid var(--line); border-radius: 24px; background: linear-gradient(120deg, rgba(35, 66, 100, .72), rgba(17, 28, 46, .82)); }
.eyebrow { color: var(--accent); font-size: .74rem; font-weight: 800; letter-spacing: .13em; margin: 0 0 8px; }
h1, h2, h3, p { margin-top: 0; }
h1 { font-size: clamp(2rem, 4vw, 3.25rem); line-height: 1.12; letter-spacing: -.035em; margin-bottom: 12px; }
.intro-copy { max-width: 760px; color: #c5d5e9; font-size: 1.05rem; margin-bottom: 18px; }
.learning-chips { display: flex; flex-wrap: wrap; gap: 8px; }
.learning-chips span { border: 1px solid rgba(119, 200, 255, .25); background: rgba(119, 200, 255, .08); color: #d9efff; border-radius: 999px; padding: 5px 11px; font-size: .8rem; }
.step-navigation { display: grid; grid-template-columns: repeat(5, 1fr); gap: 8px; margin: 18px 0; }
.step-button { min-width: 0; border: 1px solid var(--line); border-radius: 13px; background: rgba(17, 28, 46, .72); color: var(--muted); padding: 10px 8px; display: flex; justify-content: center; align-items: center; gap: 8px; }
.step-button span { display: grid; place-items: center; width: 26px; height: 26px; border-radius: 50%; border: 1px solid var(--line); font-size: .8rem; }
.step-button b { font-size: .88rem; font-weight: 650; }
.step-button.active { background: #1b3651; border-color: rgba(119, 200, 255, .6); color: white; }
.step-button.active span { background: var(--accent); color: #081423; border-color: transparent; }
.step-button.completed span { border-color: var(--good); color: var(--good); }
.lesson-layout { display: grid; grid-template-columns: minmax(0, 1.7fr) minmax(270px, .8fr); gap: 18px; align-items: start; }
.lesson-card, .side-card, .quiz-panel { border: 1px solid var(--line); background: rgba(17, 28, 46, .92); border-radius: var(--radius); padding: clamp(18px, 2.5vw, 28px); min-width: 0; }
.lesson-heading h2, .side-card h2, .quiz-panel h2 { font-size: clamp(1.3rem, 2vw, 1.75rem); letter-spacing: -.02em; line-height: 1.25; margin-bottom: 10px; }
.lesson-description { color: #c2d0e2; min-height: 52px; }
.apparatus-wrap { background: linear-gradient(180deg, rgba(7, 15, 27, .85), rgba(18, 35, 54, .85)); border: 1px solid var(--line); border-radius: 14px; overflow: hidden; }
#apparatus { display: block; width: 100%; height: auto; color: #c8d7e8; }
.svg-label { fill: currentColor; font-size: 12px; font-weight: 700; letter-spacing: .02em; }
.svg-small { fill: currentColor; opacity: .75; font-size: 10px; }
.hidden { display: none !important; }
.observation-banner { margin: 12px 0 20px; border-left: 3px solid var(--gold); background: rgba(245, 185, 66, .08); padding: 11px 13px; border-radius: 0 10px 10px 0; color: #f4dfb4; font-size: .92rem; }
.control-panel { border-top: 1px solid var(--line); padding-top: 18px; }
.control-heading { display: flex; justify-content: space-between; align-items: center; gap: 12px; }
.control-heading h3 { font-size: 1rem; margin-bottom: 12px; }
.text-button { border: 0; background: transparent; color: var(--accent); font-size: .84rem; padding: 4px; }
.control-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 18px 22px; }
.control-item label { display: flex; align-items: center; justify-content: space-between; gap: 8px; font-weight: 650; font-size: .9rem; }
.control-item output { color: var(--accent); font-variant-numeric: tabular-nums; }
.control-item input[type="range"] { display: block; width: 100%; margin: 13px 0 5px; cursor: pointer; }
.range-labels { display: flex; justify-content: space-between; color: var(--muted); font-size: .72rem; }
.metal-control { grid-column: 1 / -1; }
.metal-control select { width: 100%; margin: 8px 0 4px; border: 1px solid var(--line); border-radius: 9px; padding: 10px 12px; color: var(--text); background: #0c1728; }
.metal-control small { color: var(--muted); }
.results-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 9px; margin-top: 18px; }
.result-tile { background: var(--panel-soft); border: 1px solid var(--line); border-radius: 11px; padding: 12px; }
.result-tile span { display: block; color: var(--muted); font-size: .77rem; margin-bottom: 4px; }
.result-tile strong { font-size: 1.05rem; font-variant-numeric: tabular-nums; }
.threshold-note { margin: 12px 0 0; color: var(--good); font-size: .88rem; }
.threshold-note.no-emission { color: var(--bad); }
.lesson-footer { display: flex; justify-content: space-between; align-items: center; gap: 10px; margin-top: 22px; }
#step-count { color: var(--muted); font-size: .82rem; white-space: nowrap; }
.primary-button, .secondary-button { border-radius: 10px; padding: 10px 15px; border: 1px solid transparent; font-weight: 750; font-size: .9rem; }
.primary-button { background: var(--accent); color: #071421; }
.primary-button:hover { background: #a1ddff; }
.secondary-button { border-color: var(--line); color: var(--text); background: transparent; }
.secondary-button:disabled { opacity: .4; cursor: not-allowed; }
.side-card { position: sticky; top: 18px; }
.side-card h2 { font-size: 1.35rem; }
.side-card > p:not(.eyebrow) { color: #c2d0e2; font-size: .92rem; }
.equation-card { border: 1px solid rgba(184, 164, 255, .35); border-radius: 13px; padding: 15px; background: rgba(184, 164, 255, .08); margin: 18px 0; }
.equation-card span, .equation-card small { display: block; color: var(--muted); font-size: .78rem; }
.equation-card strong { display: block; font-size: 1.65rem; color: #ded4ff; margin: 7px 0; }
.fact-list { display: grid; gap: 14px; }
.fact-list > div { display: flex; align-items: flex-start; gap: 10px; }
.fact-list p { margin: 0; font-size: .85rem; color: var(--muted); }
.fact-list b { color: var(--text); }
.fact-dot { width: 10px; height: 10px; border-radius: 50%; margin-top: 6px; flex: 0 0 auto; }
.gold { background: var(--gold); }.teal { background: var(--teal); }.violet { background: var(--violet); }
.progress-wrap { border-top: 1px solid var(--line); margin-top: 22px; padding-top: 16px; }
.progress-label { display: flex; justify-content: space-between; font-size: .82rem; margin-bottom: 8px; }.progress-label span { color: var(--muted); }
.progress-track { height: 7px; border-radius: 999px; background: #26354a; overflow: hidden; }.progress-fill { height: 100%; width: 20%; background: linear-gradient(90deg, var(--accent), var(--teal)); transition: width .25s ease; }
.quiz-panel { margin-top: 18px; }.quiz-panel > p:not(.eyebrow) { color: var(--muted); }
.quiz-question { border: 1px solid var(--line); border-radius: 12px; margin: 16px 0; padding: 14px; min-width: 0; }
.quiz-question legend { padding: 0 6px; font-weight: 700; }
.quiz-question label { display: block; padding: 7px 4px; color: #d1deed; cursor: pointer; }
.quiz-question input { margin-right: 8px; accent-color: var(--accent); }
.quiz-feedback { min-height: 0; margin: 5px 0 0; font-size: .88rem; }.quiz-feedback.correct { color: var(--good); }.quiz-feedback.incorrect { color: var(--bad); }
.quiz-score { margin: 12px 0 0; font-weight: 750; }
.module-footer { border-top: 1px solid var(--line); margin-top: 24px; padding-top: 16px; color: var(--muted); font-size: .8rem; }.module-footer p { margin: 4px 0; }
@media (max-width: 850px) { .lesson-layout { grid-template-columns: 1fr; }.side-card { position: static; }.side-card .fact-list { grid-template-columns: repeat(3, 1fr); }.side-card .fact-list > div { gap: 7px; } }
@media (max-width: 560px) { .module-header { align-items: flex-start; flex-direction: column; gap: 6px; }.site-label span { display: block; font-size: .8rem; }.step-navigation { gap: 5px; }.step-button { flex-direction: column; padding: 8px 3px; gap: 4px; }.step-button b { font-size: .7rem; }.step-button span { width: 23px; height: 23px; }.control-grid { grid-template-columns: 1fr; }.metal-control { grid-column: auto; }.side-card .fact-list { grid-template-columns: 1fr; }.lesson-footer { flex-wrap: wrap; }.lesson-footer .primary-button, .lesson-footer .secondary-button { padding: 9px 11px; }.results-grid { gap: 7px; }.result-tile { padding: 10px; }.result-tile strong { font-size: .95rem; } }
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { scroll-behavior: auto !important; transition-duration: .01ms !important; animation-duration: .01ms !important; } }

/* Planck's-constant graph: these styles belong only to this standalone module. */
.planck-graph-card { margin-top: 22px; padding: clamp(16px, 2.4vw, 24px); border: 1px solid var(--line); border-radius: 16px; background: rgba(13, 23, 39, .72); }
.graph-heading { display: flex; justify-content: space-between; align-items: flex-start; gap: 14px; }
.graph-heading h3 { font-size: clamp(1.12rem, 2vw, 1.45rem); line-height: 1.3; margin-bottom: 8px; }
.graph-tag { flex: 0 0 auto; padding: 4px 9px; border: 1px solid rgba(105, 213, 194, .35); border-radius: 999px; color: var(--teal); font-size: .72rem; font-weight: 750; }
.graph-intro, .graph-explanation { color: #c2d0e2; font-size: .9rem; }
.graph-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: 12px; background: #0b1525; }
#planck-graph { display: block; width: 100%; min-width: 470px; height: auto; }
.graph-grid-line { stroke: rgba(180, 202, 229, .13); stroke-width: 1; }
.graph-zero-line { stroke: rgba(230, 239, 250, .38); stroke-width: 1.3; }
.graph-axis-line { stroke: #bdcde0; stroke-width: 1.5; }
.graph-tick { fill: #aabbd1; font-size: 11px; }
.graph-axis-label { fill: #e6f0fc; font-size: 12px; font-weight: 700; }
.planck-line { fill: none; stroke: #77c8ff; stroke-width: 3.5; stroke-linejoin: round; stroke-linecap: round; }
.threshold-marker { stroke: #f5b942; stroke-width: 1.5; stroke-dasharray: 5 5; }
.threshold-point { fill: #f5b942; stroke: #fff0c4; stroke-width: 1.5; }
.current-point { fill: #69d5c2; stroke: #e1fff7; stroke-width: 2; }
.no-emission-point { fill: #ffad9e; stroke: #fff0ec; }
.graph-annotation { fill: #f3e3b7; font-size: 11px; font-weight: 750; }
.slope-triangle { fill: rgba(119, 200, 255, .08); stroke: #b8a4ff; stroke-width: 1.5; stroke-dasharray: 4 3; }
.planck-results { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 9px; margin: 13px 0; }
.planck-result { min-width: 0; padding: 12px; border: 1px solid var(--line); border-radius: 10px; background: var(--panel-soft); }
.planck-result span { display: block; color: var(--muted); font-size: .76rem; margin-bottom: 5px; }
.planck-result strong { display: block; font-size: clamp(.86rem, 1.6vw, 1.02rem); overflow-wrap: anywhere; color: var(--teal); font-variant-numeric: tabular-nums; }
.graph-explanation { margin: 10px 0 14px; }
.graph-takeaway { border-left: 3px solid var(--violet); padding: 12px 14px; background: rgba(184, 164, 255, .07); border-radius: 0 10px 10px 0; font-size: .87rem; }
.graph-takeaway ol { margin: 8px 0 0; padding-left: 22px; color: #c2d0e2; }
.graph-takeaway li + li { margin-top: 4px; }
@media (max-width: 560px) { .planck-results { grid-template-columns: 1fr; }.graph-heading { flex-direction: column; }.graph-tag { align-self: flex-start; } }