/* ======================================== */
/* STUDYNEST VARIATION LESSONS                  */
/* ======================================== */

:root {
    --navy: #0f438c;
    --navy-dark: #0a326b;
    --blue: #2f78bc;
    --blue-light: #e1f0fb;
    --page: #eef4fb;
    --card: #ffffff;
    --border: #d9e2ed;
    --text: #1e2c43;
    --muted: #4f5d70;
    --yellow: #fff2bf;
    --yellow-border: #f5ad00;
    --green: #e4f5e8;
    --green-dark: #2f7444;
    --pink: #f8e8ef;
    --pink-dark: #8b4664;
    --purple: #eee8f8;
    --purple-dark: #654d91;
    --shadow: 0 12px 30px rgba(19, 57, 104, 0.07);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
    margin: 0;
    color: var(--text);
    background: var(--page);
    font-family: Arial, Helvetica, sans-serif;
    line-height: 1.65;
}

a { color: inherit; text-decoration: none; }

.announcement-bar {
    padding: 8px 18px;
    color: #111;
    background: #f7b500;
    font-size: .82rem;
    font-weight: 700;
    text-align: center;
}

.site-header {
    display: flex;
    min-height: 76px;
    padding: 0 38px;
    align-items: center;
    justify-content: space-between;
    gap: 30px;
    border-bottom: 1px solid var(--border);
    background: white;
}

.logo {
    color: var(--navy);
    font-size: 1.45rem;
    font-weight: 800;
}

.main-navigation {
    display: flex;
    flex-wrap: wrap;
    gap: 24px;
}

.main-navigation a {
    font-size: .88rem;
    font-weight: 700;
}

.lesson-hero {
    display: grid;
    min-height: 400px;
    padding: 60px clamp(22px, 7vw, 95px);
    align-items: center;
    grid-template-columns: minmax(0, 1.1fr) minmax(310px, .9fr);
    gap: 45px;
    background:
        radial-gradient(circle at 85% 15%, rgba(255,255,255,.95), transparent 26%),
        linear-gradient(135deg, #f8fbff, #eaf2fb);
}

.lesson-label,
.eyebrow {
    margin: 0 0 10px;
    color: var(--navy);
    font-size: .78rem;
    font-weight: 900;
    letter-spacing: .12em;
    text-transform: uppercase;
}

.lesson-hero h1 {
    margin: 0;
    color: var(--navy);
    font-size: clamp(2.9rem, 6vw, 4.8rem);
    line-height: 1.04;
    letter-spacing: -.04em;
}

.lesson-subtitle {
    max-width: 680px;
    margin: 20px 0 0;
    color: var(--muted);
    font-size: 1.08rem;
}

.lesson-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    margin-top: 24px;
}

.meta-pill {
    padding: 8px 13px;
    border: 1px solid var(--border);
    border-radius: 999px;
    color: var(--navy);
    background: white;
    font-size: .78rem;
    font-weight: 800;
}

.hero-visual {
    display: grid;
    min-height: 270px;
    place-items: center;
}

.mini-coordinate-plane {
    position: relative;
    width: 290px;
    height: 245px;
    border: 1px solid var(--border);
    border-radius: 25px;
    background:
        linear-gradient(#dfe8f2 1px, transparent 1px),
        linear-gradient(90deg, #dfe8f2 1px, transparent 1px),
        white;
    background-size: 32px 32px;
    box-shadow: var(--shadow);
}

.mini-coordinate-plane::before,
.mini-coordinate-plane::after {
    content: "";
    position: absolute;
    background: var(--navy);
}

.mini-coordinate-plane::before {
    top: 20px;
    bottom: 20px;
    left: 50%;
    width: 3px;
}

.mini-coordinate-plane::after {
    right: 20px;
    bottom: 50%;
    left: 20px;
    height: 3px;
}

.plot-dot {
    position: absolute;
    z-index: 2;
    width: 15px;
    height: 15px;
    border: 3px solid white;
    border-radius: 50%;
    background: var(--blue);
    box-shadow: 0 3px 9px rgba(15,67,140,.25);
}

.dot-a { left: 205px; top: 55px; }
.dot-b { left: 75px; top: 155px; }
.dot-c { left: 180px; top: 180px; }

.graph-line-demo {
    position: absolute;
    z-index: 1;
    left: 55px;
    bottom: 65px;
    width: 205px;
    height: 5px;
    border-radius: 999px;
    background: var(--blue);
    transform: rotate(-36deg);
    transform-origin: left center;
}

.lesson-main {
    width: min(1180px, calc(100% - 28px));
    margin: 36px auto 70px;
}

.lesson-section {
    margin-bottom: 28px;
    padding: 38px 52px;
    border: 1px solid var(--border);
    border-radius: 27px;
    background: white;
    box-shadow: var(--shadow);
}

.lesson-section h2 {
    margin: 0 0 18px;
    color: var(--navy);
    font-size: clamp(1.65rem, 3vw, 2.25rem);
}

.lesson-section h3 {
    margin: 25px 0 10px;
    color: var(--navy);
}

.lesson-section p { color: var(--muted); }

.objective-list,
.summary-list,
.practice-list {
    margin: 14px 0 0;
    padding-left: 24px;
}

.objective-list li,
.summary-list li,
.practice-list li {
    margin: 8px 0;
}

.think-box,
.key-idea,
.tip-box,
.warning-box,
.did-you-know,
.challenge-box {
    margin: 22px 0;
    padding: 20px 23px;
    border-radius: 0 17px 17px 0;
}

.think-box {
    border-left: 5px solid var(--yellow-border);
    background: var(--yellow);
}

.key-idea {
    border-left: 5px solid var(--blue);
    background: #eaf3ff;
}

.tip-box {
    border-left: 5px solid #54a46a;
    background: var(--green);
}

.warning-box {
    border-left: 5px solid #d5648f;
    background: var(--pink);
}

.did-you-know {
    border-left: 5px solid #8367b2;
    background: var(--purple);
}

.challenge-box {
    border-left: 5px solid #815a20;
    background: #f9eddc;
}

.math-display {
    margin: 20px 0;
    padding: 17px;
    border: 1px solid var(--border);
    border-radius: 15px;
    color: var(--navy);
    background: #f8fbff;
    font-size: 1.18rem;
    font-weight: 800;
    text-align: center;
}

.visual-grid-two {
    display: grid;
    grid-template-columns: repeat(2, minmax(0,1fr));
    gap: 20px;
    margin-top: 22px;
}

.visual-card {
    padding: 24px;
    border: 1px solid var(--border);
    border-radius: 21px;
    background: #f9fbfd;
}

.visual-card h3 { margin-top: 0; }

.coordinate-diagram,
.travel-diagram,
.line-diagram {
    position: relative;
    width: min(100%, 480px);
    height: 310px;
    margin: 24px auto;
    border: 1px solid var(--border);
    border-radius: 22px;
    background:
        linear-gradient(#dde7f1 1px, transparent 1px),
        linear-gradient(90deg, #dde7f1 1px, transparent 1px),
        white;
    background-size: 35px 35px;
    overflow: hidden;
}

.axis-x,
.axis-y {
    position: absolute;
    z-index: 2;
    background: var(--navy);
}

.axis-x {
    left: 25px;
    right: 25px;
    top: 50%;
    height: 3px;
}

.axis-y {
    top: 25px;
    bottom: 25px;
    left: 50%;
    width: 3px;
}

.axis-label {
    position: absolute;
    z-index: 3;
    color: var(--navy);
    font-weight: 900;
}

.x-label { right: 12px; top: calc(50% - 24px); }
.y-label { left: calc(50% + 10px); top: 8px; }

.quadrant {
    position: absolute;
    color: #7c8b9d;
    font-size: .75rem;
    font-weight: 800;
}

.q1 { right: 52px; top: 42px; }
.q2 { left: 52px; top: 42px; }
.q3 { left: 52px; bottom: 42px; }
.q4 { right: 52px; bottom: 42px; }

.example-table {
    width: 100%;
    margin: 22px 0;
    border-collapse: collapse;
    overflow: hidden;
    border-radius: 14px;
}

.example-table th,
.example-table td {
    padding: 13px;
    border: 1px solid var(--border);
    text-align: center;
}

.example-table th {
    color: white;
    background: var(--navy);
}

.example-table tr:nth-child(even) td {
    background: #f5f8fc;
}

.worked-example {
    margin: 22px 0;
    padding: 24px;
    border: 1px solid var(--border);
    border-radius: 20px;
    background: #fbfcfe;
}

.worked-example h3 { margin-top: 0; }

.step {
    display: grid;
    grid-template-columns: 42px minmax(0,1fr);
    gap: 14px;
    margin-top: 16px;
    align-items: start;
}

.step-number {
    display: grid;
    width: 38px;
    height: 38px;
    place-items: center;
    border-radius: 50%;
    color: white;
    background: var(--navy);
    font-weight: 900;
}

.quick-check {
    display: grid;
    grid-template-columns: repeat(3, minmax(0,1fr));
    gap: 15px;
    margin-top: 20px;
}

.quick-card {
    padding: 20px;
    border: 1px solid var(--border);
    border-radius: 18px;
    background: #f9fbfd;
}

.level-heading {
    display: inline-flex;
    margin: 22px 0 8px;
    padding: 7px 12px;
    border-radius: 999px;
    color: var(--navy);
    background: var(--blue-light);
    font-size: .75rem;
    font-weight: 900;
}

.lesson-navigation {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 15px;
    margin-top: 34px;
}

.nav-button {
    display: flex;
    min-height: 52px;
    padding: 12px 18px;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--border);
    border-radius: 999px;
    color: var(--navy);
    background: white;
    font-weight: 800;
    text-align: center;
}

.nav-button.primary {
    color: white;
    background: var(--navy);
}

.site-footer {
    padding: 34px 20px 24px;
    color: white;
    background: var(--navy);
    text-align: center;
}

.site-footer p { margin: 8px 0; font-size: .82rem; }

@media (max-width: 900px) {
    .lesson-hero { grid-template-columns: 1fr; }
    .visual-grid-two { grid-template-columns: 1fr; }
    .quick-check { grid-template-columns: 1fr; }
}

@media (max-width: 700px) {
    .site-header {
        padding: 18px 20px;
        align-items: flex-start;
        flex-direction: column;
    }

    .lesson-hero {
        padding: 45px 23px;
        text-align: center;
    }

    .lesson-meta { justify-content: center; }
    .lesson-section { padding: 28px 23px; }
    .lesson-navigation { grid-template-columns: 1fr; }
}
/* ======================================== */
/* VARIATION-SPECIFIC COMPONENTS            */
/* ======================================== */

.relationship-flow {
    display: grid;
    grid-template-columns: minmax(120px, 1fr) auto minmax(120px, 1fr);
    align-items: center;
    gap: 18px;
    margin: 24px 0;
}

.relationship-box {
    padding: 22px;
    border: 1px solid var(--border);
    border-radius: 19px;
    color: var(--navy);
    background: #f8fbff;
    font-size: 1.05rem;
    font-weight: 800;
    text-align: center;
}

.relationship-arrow {
    color: var(--blue);
    font-size: 2rem;
    font-weight: 900;
}

.ratio-strip {
    display: grid;
    grid-template-columns: repeat(4, minmax(80px, 1fr));
    gap: 12px;
    margin: 22px 0;
}

.ratio-strip div {
    padding: 17px 12px;
    border: 1px solid var(--border);
    border-radius: 16px;
    background: #f9fbfd;
    text-align: center;
}

.ratio-strip strong {
    display: block;
    color: var(--navy);
    font-size: 1.1rem;
}

.recognition-box {
    margin: 22px 0;
    padding: 21px 24px;
    border-left: 5px solid #7b68b0;
    border-radius: 0 17px 17px 0;
    background: #eee8f8;
}

.recognition-box h3 {
    margin-top: 0;
    color: #5c4788;
}

.answers-section details {
    margin-top: 18px;
    overflow: hidden;
    border: 1px solid var(--border);
    border-radius: 18px;
    background: #f9fbfd;
}

.answers-section summary {
    padding: 18px 22px;
    color: var(--navy);
    font-weight: 800;
    cursor: pointer;
    list-style-position: inside;
}

.answers-section summary:hover {
    background: #f1f6fc;
}

.answers-content {
    padding: 5px 24px 24px;
    border-top: 1px solid var(--border);
}

.answers-content h3 {
    margin-top: 22px;
}

.answers-content ol {
    padding-left: 24px;
}

.answers-content li {
    margin: 10px 0;
    color: var(--muted);
}

.answer-working {
    margin-top: 7px;
    padding: 10px 13px;
    border-radius: 12px;
    color: var(--text);
    background: white;
}

@media (max-width: 700px) {
    .relationship-flow {
        grid-template-columns: 1fr;
    }

    .relationship-arrow {
        transform: rotate(90deg);
        text-align: center;
    }

    .ratio-strip {
        grid-template-columns: repeat(2, minmax(80px, 1fr));
    }
}


/* =========================================================
   Variation interactive learning boards
   Added after the original StudyNest stylesheet. Existing
   selectors above are unchanged.
   ========================================================= */
.variation-real-life{overflow:hidden}.variation-board{display:grid;grid-template-columns:minmax(250px,.88fr) minmax(330px,1.12fr);gap:24px;align-items:center}.variation-controls{min-width:0}.variation-slider-label{display:flex;justify-content:space-between;gap:12px;font-weight:800;margin:13px 0 7px;color:var(--navy)}.variation-controls input[type=range],.variation-mini-board input[type=range]{width:100%;accent-color:var(--blue)}.variation-graph-panel{border:1px solid var(--border);border-radius:18px;padding:10px;background:#fff;box-shadow:0 8px 24px rgba(30,55,82,.06)}.variation-svg{width:100%;height:auto;display:block}.variation-svg .grid-line{stroke:#dce6f0;stroke-width:1}.variation-svg .axis-line{stroke:var(--navy);stroke-width:2.2}.variation-svg .tick-label,.variation-svg .axis-label,.variation-svg .coordinate-label{fill:var(--navy);font-family:inherit;font-size:13px}.variation-svg .axis-label{font-weight:900}.variation-svg .graph-line{fill:none;stroke:var(--blue);stroke-width:4;stroke-linecap:round}.variation-svg .point{fill:var(--blue);stroke:#fff;stroke-width:2}.variation-svg .selected-point{fill:#f5b800;stroke:var(--navy);stroke-width:2.5}.variation-svg .guide{stroke:#7893ad;stroke-dasharray:5 4}.variation-live-cards{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin-top:14px}.variation-live-cards div{border:1px solid var(--border);border-radius:14px;padding:12px;text-align:center;background:#fff}.variation-live-cards span{display:block;font-size:.86rem;color:var(--muted)}.variation-live-cards strong{font-size:1.35rem;color:var(--navy)}.variation-live-table{margin-top:20px}.interaction-note{padding:12px 15px;border-radius:14px;background:#f4f8fc;color:var(--navy)}.variation-actions{display:flex;flex-wrap:wrap;gap:10px;margin-top:14px}.variation-actions button{border:1px solid var(--border);border-radius:999px;padding:10px 15px;background:#fff;color:var(--navy);font:inherit;font-weight:800;cursor:pointer}.variation-actions button:hover{background:#f4f8fc}.variation-pattern-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px}.variation-mini-board{border:1px solid var(--border);border-radius:18px;padding:18px;background:#fff}.variation-arrow-pair{display:flex;flex-wrap:wrap;align-items:center;justify-content:center;gap:10px;padding:12px;border-radius:14px;background:#f4f8fc;margin:12px 0}.variation-arrow-pair span{display:grid;gap:3px;text-align:center}.variation-arrow-pair strong{color:var(--blue);font-size:1.5rem}.variation-result{font-weight:900;color:var(--navy);margin-bottom:0}.variation-hero-demo{display:grid;gap:12px}.hero-relation{display:grid;grid-template-columns:1fr auto 1fr;gap:8px;align-items:center;padding:14px;border:1px solid rgba(255,255,255,.45);border-radius:16px;background:rgba(255,255,255,.13);text-align:center}.hero-relation span{font-weight:900}.hero-relation small{grid-column:1/-1}.hero-arrow-up{font-size:1.8rem;animation:variationPulse 1.5s infinite}.inverse-hero-relation span:last-of-type{animation:variationFade 1.5s infinite alternate}@keyframes variationPulse{50%{transform:translateY(-5px)}}@keyframes variationFade{to{transform:translateY(5px);opacity:.62}}.chocolate-visual{display:flex;flex-wrap:wrap;gap:10px;justify-content:center;align-content:center;min-height:230px;padding:20px}.chocolate-bar{width:42px;height:70px;border:3px solid #6b452f;border-radius:8px;background:repeating-linear-gradient(90deg,#9a6745 0 12px,#7d5137 12px 14px);box-shadow:inset 0 0 0 3px #b88662}.rectangle-stage{min-height:320px;display:grid;place-items:center;position:relative;padding:35px}.floor-rectangle{display:grid;place-items:center;background:repeating-linear-gradient(0deg,transparent 0 28px,rgba(255,255,255,.68) 28px 30px),repeating-linear-gradient(90deg,#cde9ff 0 28px,#fff 28px 30px);border:3px solid var(--blue);border-radius:10px;transition:width .18s,height .18s}.floor-rectangle span{background:#fff;border:1px solid var(--border);border-radius:999px;padding:6px 10px;font-weight:900}.length-caption,.width-caption{position:absolute;font-weight:900;color:var(--navy)}.length-caption{bottom:10px;left:50%;transform:translateX(-50%)}.width-caption{right:8px;top:50%;transform:translateY(-50%) rotate(90deg)}.fare-parts{display:flex;flex-wrap:wrap;align-items:center;justify-content:center;gap:10px;margin:16px 0}.fare-parts div{border:1px solid var(--border);border-radius:14px;padding:10px 14px;text-align:center;background:#fff}.fare-parts span{display:block;font-size:.82rem;color:var(--muted)}.fare-parts strong{font-size:1.25rem;color:var(--navy)}.scenario-ribbon{display:flex;flex-wrap:wrap;gap:12px;align-items:center;justify-content:center;margin-top:18px;padding:16px;border-radius:16px;background:#f4f8fc;color:var(--navy);font-weight:800}.scenario-ribbon strong{color:var(--blue)}
@media(max-width:800px){.variation-board,.variation-pattern-grid{grid-template-columns:1fr}.variation-graph-panel{padding:5px}.rectangle-stage{min-height:270px}.hero-relation{grid-template-columns:1fr auto 1fr}}