:root {
    --primary: #0057b7;
    --accent: #ffd700;
    --bg: #f4f7f9;
    --text: #333;
    --gap-x: clamp(1px, 2vw, 15px);
}

* {
    box-sizing: border-box;
    font-family: 'Segoe UI', sans-serif;
}

body.trainer {
    background-color: #f0f2f5;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    padding: var(--gap-x);
}

.trainer .container {
    background-color: #ffffff;
    border-radius: 16px;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.1);
    padding: 40px var(--gap-x);
    width: 100%;
    max-width: 1280px;
    text-align: center;
    position: relative;
}

.trainer .counter-badge {
    position: absolute;
    top: 20px;
    right: 20px;
    background-color: #e2e8f0;
    color: #475569;
    padding: 8px 16px;
    border-radius: 20px;
    font-size: 1rem;
    font-weight: bold;
    cursor: pointer;
}

.trainer h1 {
    color: #1e293b;
    font-size: 1.8rem;
    margin-top: 25px;
    margin-bottom: 25px;
}

.trainer .control-panel {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 10px;
    margin-bottom: 30px;
}

.trainer .tabs {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 10px;
    flex-wrap: wrap;
    width: 100%;
    margin-bottom: 0;
}

.trainer .tab-btn {
    background-color: #f1f5f9;
    color: #475569;
    border: 2px solid #cbd5e1;
    border-radius: 8px;
    padding: 10px 15px;
    font-size: 1.1rem;
    cursor: pointer;
}

.page-factors .tab-btn {
    font-weight: 500;
}
.trainer .tab-btn.active {
    background-color: #2563eb;
    color: white;
    border-color: #2563eb;
}

/* factors.html emphasized buttons (visual, kept) */
.trainer .tab-btn.tb-bold {
    font-weight: 800;
    border-color: #94a3b8;
}
.trainer .tab-btn.tb-bold.active {
    background-color: #1d4ed8;
    border-color: #1d4ed8;
}

/* Sub-label used by equations.html system row */
.trainer .sub-lbl {
    font-size: 1.1rem;
    font-weight: 500;
    color: #475569;
    padding-right: 5px;
}

/* Options block (expressions.html) */
.trainer .options {
    display: flex;
    gap: 20px;
    flex-wrap: wrap;
    justify-content: center;
}
.trainer .checkbox-container {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.1rem;
    font-weight: 600;
    color: #1e293b;
    cursor: pointer;
    background-color: #fff7ed;
    border: 2px dashed #f97316;
    padding: 10px 15px;
    border-radius: 8px;
}
.trainer .checkbox-container.inverse {
    background-color: #f0fdf4;
    border-color: #10b981;
}
.trainer .checkbox-container input {
    width: 20px;
    height: 20px;
    cursor: pointer;
}

.trainer .equation-container {
    overflow-x: auto;
    white-space: nowrap;
    background-color: #f8fafc;
    border: 2px solid #e2e8f0;
    border-radius: 12px;
    padding: 30px var(--gap-x);
    margin-bottom: 30px;
}

.trainer .equation-display {
    font-weight: bold;
    color: #0f172a;
}
/* font-size / display / alignment are visual, kept per-page */
.page-equations .equation-display {
    font-size: 1.9rem;
    display: block;
    text-align: left;
}
.page-factors .equation-display {
    font-size: 2.2rem;
    display: inline-block;
    vertical-align: middle;
}
.page-expressions .equation-display {
    font-size: 3.5rem;
    display: inline-block;
}

/* Inline math tokens */
.trainer .variable,
.trainer .v-x { color: #2563eb; font-style: italic; }
.trainer .v-y,
.trainer .vl { color: #8b5cf6; padding-right: 3px; }
.trainer .v-y { font-style: italic; }
.trainer .sign { color: #f97316; font-weight: bold; padding: 0 4px; }

/* equations.html system rendering */
.trainer .sys-bracket {
    font-size: 4.5rem;
    color: #475569;
    vertical-align: middle;
    margin-right: 5px;
    display: inline-block;
    line-height: 1;
    font-weight: 300;
}
.trainer .sys-block {
    display: inline-block;
    vertical-align: middle;
    text-align: left;
    line-height: 1.4;
}
.trainer .step-row {
    display: grid;
    grid-template-columns: 280px 1fr;
    margin-bottom: 12px;
    align-items: start;
    white-space: normal;
}
.trainer .step-lbl {
    text-align: right;
    padding-right: 15px;
    color: #475569;
    font-weight: 600;
    font-size: 1.3rem;
    border-right: 3px solid #cbd5e1;
}
.trainer .step-val {
    padding-left: 15px;
    font-size: 1.8rem;
}

/* factors.html arithmetic / fraction rendering */
.trainer .nm { color: #2563eb; }
.trainer .lb {
    font-size: 1.7rem;
    color: #475569;
    font-weight: 600;
    padding: 0 4px;
}
.trainer .fr {
    display: inline-flex;
    flex-direction: column;
    vertical-align: middle;
    align-items: center;
    padding: 0 2px;
}
.trainer .nu {
    border-bottom: 4px solid #f97316;
    padding-bottom: 2px;
    line-height: 1;
}
.trainer .de {
    padding-top: 4px;
    line-height: 1;
}
.trainer .mp {
    font-size: 1.2rem;
    color: #10b981;
    vertical-align: super;
    font-weight: bold;
}
.trainer s { color: #ef4444; text-decoration: line-through; font-weight: bold; }
.trainer s .nm, .trainer s .vl { color: #ef4444; }
.trainer .hc {
    text-decoration: underline;
    text-decoration-style: wavy;
    text-decoration-color: #10b981;
    text-underline-offset: 4px;
    display: inline-block;
}

/* Primary action button */
.trainer .btn {
    background-color: #10b981;
    color: white;
    border: none;
    border-radius: 12px;
    padding: 18px 36px;
    font-size: 1.4rem;
    font-weight: 600;
    cursor: pointer;
    width: 100%;
    max-width: 350px;
}
/* equations.html centered its button explicitly (layout, kept) */
.page-equations .btn {
    display: block;
    margin: 0 auto;
}
.trainer .btn:hover { background-color: #059669; }

/* ============================================================
   Landing page (index.html)
   Kept close to the trainer design system.
   ============================================================ */
body.home {
    background-color: var(--bg);
    color: var(--text);
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    align-items: center;
    justify-content: center;
}
.home .container {
    max-width: 1200px;
    width: 90%;
    text-align: center;
    padding: 20px;
}
.home h1 {
    color: var(--primary);
    font-size: 2.5rem;
    margin-bottom: 10px;
}
.home .subtitle {
    font-size: 1.2rem;
    color: #666;
    margin-bottom: 40px;
}
.home .grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 25px;
}
.home .card {
    background: white;
    border-radius: 12px;
    padding: 30px 20px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.05);
    text-decoration: none;
    color: var(--text);
    transition: transform 0.3s ease, box-shadow 0.3s ease, border-color 0.3s ease;
    border: 2px solid transparent;
    display: flex;
    flex-direction: column;
    align-items: center;
}
.home .card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0, 55, 183, 0.15);
    border-color: var(--primary);
}
.home .icon-box {
    width: 80px;
    height: 80px;
    background-color: #e6f0fa;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary);
}
.home .icon-box.fraction { font-size: 2rem; }
.home .icon-box.divisibility { letter-spacing: -0.5px; }

.home .card h2 {
    font-size: 1.4rem;
    margin: 10px 0;
    color: #111;
}
.home .card p {
    font-size: 0.95rem;
    color: #666;
    line-height: 1.4;
}
.home footer {
    margin-top: 50px;
    font-size: 0.9rem;
    color: #999;
}

/* ============================================================
   Divisibility page (division.html)
   Reuses factors.html tokens (.nm, .vl, .sign) and <s> for the
   "not divisible" mark; only layout and the dot picker are new.
   ============================================================ */
.page-division .equation-display {
    font-size: 2.2rem;
    display: block;
    text-align: left;
    line-height: 1.8;
}
.page-division .ok { color: #10b981; font-weight: bold; }
.page-division table { border-collapse: collapse; }
.page-division td { padding: 0; vertical-align: top; }

.page-division .digit-picker {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-left: 20px;
    cursor: pointer;
}
.page-division .dot-mark {
    font-size: 1.8rem;
    line-height: 1;
    color: #cbd5e1;
}
.page-division .dot input { position: absolute; opacity: 0; }
.page-division .dot input:checked + .dot-mark { color: #2563eb; }