/* ============================================================
   MINH DUONG MATH — Trang Phương Pháp
   Mobile-First · clamp() / auto-fit responsive
   ============================================================ */

/* ── SECTION PADDING SCALE ───────────────────────────────────── */
.methodology-section { background: var(--white); padding: clamp(2.5rem, 8vw, 5rem) clamp(1rem, 4%, 2.5rem); }
.diagram-section     { background: var(--primary-dark); color: var(--white); padding: clamp(2.5rem, 8vw, 5rem) clamp(1rem, 4%, 2.5rem); text-align: center; }
.benefits-section    { background: var(--cream); padding: clamp(2.5rem, 8vw, 5rem) clamp(1rem, 4%, 2.5rem); }
.cta-section         { background: linear-gradient(135deg, var(--primary-dark) 0%, var(--primary-light) 100%); color: var(--white); padding: clamp(2.5rem, 8vw, 3.75rem) clamp(1rem, 4%, 2.5rem); text-align: center; }

/* ── LEVELS GRID ─────────────────────────────────────────────── */
.levels-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: clamp(0.75rem, 2vw, 1rem);
    margin-top: clamp(1.5rem, 4vw, 2.5rem);
}

@media (min-width: 480px) { .levels-grid { grid-template-columns: repeat(2, 1fr); } }
@media (min-width: 768px) { .levels-grid { grid-template-columns: repeat(3, 1fr); } }

.level-card {
    background: var(--white);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: clamp(1rem, 3%, 1.125rem) clamp(1rem, 4%, 1.25rem);
    position: relative;
    transition: transform var(--transition), box-shadow var(--transition);
}
.level-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-card); }
.level-card--key  { border-left: 4px solid var(--primary-dark); background: linear-gradient(135deg, #f5f3ff 0%, #fff 100%); }

.level-card__num {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: clamp(24px, 5vw, 28px);
    height: clamp(24px, 5vw, 28px);
    border-radius: 50%;
    background: var(--primary-dark);
    color: var(--white);
    font-size: clamp(0.7rem, 1.5vw, 0.8125rem);
    font-weight: 700;
    margin-bottom: clamp(0.5rem, 1.5vw, 0.625rem);
}

.level-card__title   { font-size: clamp(0.875rem, 2vw, 0.9375rem); font-weight: 700; color: var(--primary-dark); margin-bottom: 6px; }
.level-card__desc    { font-size: clamp(0.75rem, 1.5vw, 0.8125rem); line-height: 1.55; color: var(--text-gray); margin-bottom: 7px; }
.level-card__example { font-size: clamp(0.6875rem, 1.3vw, 0.75rem); font-style: italic; color: var(--primary-light); border-top: 1px solid var(--border); padding-top: 7px; margin: 0; line-height: 1.5; }

/* ── DIAGRAM SECTION ─────────────────────────────────────────── */
.diagram-section h2 { color: var(--white); margin-bottom: clamp(1rem, 3vw, 1.25rem); }

.diagram-intro {
    font-size: clamp(0.875rem, 2vw, 1rem);
    margin-bottom: clamp(1.75rem, 5vw, 2.5rem);
    color: rgba(255,255,255,0.9);
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

.diagram-container {
    background: rgba(255,255,255,0.05);
    padding: clamp(1.5rem, 5vw, 2.5rem);
    border-radius: var(--radius-md);
    margin-bottom: clamp(1.75rem, 5vw, 2.5rem);
    overflow-x: auto;
}

.diagram-note {
    background: rgba(91, 163, 184, 0.1);
    padding: clamp(1rem, 3vw, 1.5rem);
    border-left: 4px solid var(--primary-light);
    border-radius: var(--radius-sm);
    text-align: left;
    color: rgba(255,255,255,0.9);
    font-size: clamp(0.8125rem, 1.5vw, 0.875rem);
    line-height: 1.8;
    max-width: 900px;
    margin: 0 auto;
}
.diagram-note strong { color: var(--white); }

/* ── BENEFITS GRID ───────────────────────────────────────────── */
.benefits-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(clamp(240px, 30%, 380px), 1fr));
    gap: clamp(0.875rem, 2.5vw, 1.875rem);
    max-width: 1100px;
    margin: 0 auto;
}

.benefit-card {
    padding: clamp(1.25rem, 4%, 2rem);
    background: var(--white);
    border-radius: var(--radius-md);
    border-top: 4px solid var(--primary-light);
    transition: all var(--transition);
}
.benefit-card:hover { transform: translateY(-8px); box-shadow: var(--shadow-hover); }
.benefit-card h4 { color: var(--primary-dark); margin-bottom: clamp(0.625rem, 2vw, 0.75rem); }
.benefit-card p  { font-size: clamp(0.8125rem, 1.5vw, 0.875rem); }

/* ── CTA SECTION ─────────────────────────────────────────────── */
.cta-section h2 { color: var(--white); margin-bottom: clamp(1rem, 3vw, 1.25rem); }
.cta-section p  {
    color: rgba(255,255,255,0.9);
    margin-bottom: clamp(1.5rem, 4vw, 1.875rem);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
    font-size: clamp(0.875rem, 2vw, 1rem);
}

/* ── TIMELINE ─────────────────────────────────────────────────── */
.timeline {
    max-width: 900px;
    margin: 0 auto;
    position: relative;
    padding: clamp(1.5rem, 4vw, 2.5rem) 0;
}

/* Mobile: single left-rail */
.timeline::before {
    content: '';
    position: absolute;
    left: 15px;
    top: 0; bottom: 0;
    width: 2px;
    background: var(--primary-light);
}

.timeline__item {
    margin-bottom: clamp(2rem, 5vw, 3.125rem);
    margin-left: clamp(2.5rem, 8vw, 3.75rem);
    padding-left: 0;
    padding-right: 0;
    text-align: left;
    position: relative;
}

.timeline__dot {
    position: absolute;
    left: 0;
    transform: translateX(-28px);
    width: clamp(24px, 5vw, 28px);
    height: clamp(24px, 5vw, 28px);
    background: var(--primary-dark);
    border: 3px solid var(--white);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    font-weight: 700;
    font-size: clamp(0.75rem, 1.5vw, 0.8125rem);
    z-index: 2;
    top: 0;
    box-shadow: 0 2px 8px rgba(74, 122, 148, 0.3);
}

.timeline__card {
    background: var(--cream);
    padding: clamp(0.875rem, 3%, 1.5rem) clamp(1rem, 4%, 1.75rem);
    border-radius: var(--radius-md);
    border-left: 4px solid var(--primary-light);
    transition: all var(--transition);
}
.timeline__card:hover { transform: translateY(-4px); box-shadow: var(--shadow-card); }
.timeline__card h3 { color: var(--primary-dark); margin-bottom: clamp(0.5rem, 2vw, 0.75rem); font-size: clamp(1rem, 2.5vw, 1.25rem); }
.timeline__card p  { font-size: clamp(0.8125rem, 1.5vw, 0.9375rem); line-height: 1.6; }

.timeline__example {
    margin-top: clamp(0.625rem, 2vw, 0.75rem);
    padding-top: clamp(0.625rem, 2vw, 0.75rem);
    border-top: 1px solid var(--border);
    font-size: clamp(0.75rem, 1.5vw, 0.875rem);
    font-style: italic;
    color: var(--primary-light);
}

/* ── Scroll reveal ───────────────────────────────────────────── */
body.js-reveals .timeline__item.reveal { transform: translateX(-16px) translateY(8px); }
body.js-reveals .timeline__item.reveal.is-visible { transform: none; }

/* ── md: 768px+ — Timeline switches to alternating left/right ── */
@media (min-width: 768px) {
    .timeline::before { left: 50%; transform: translateX(-50%); }
    .timeline__item   { margin-left: 0; }
    .timeline__item:nth-child(odd)  { padding-right: 52%; text-align: right; }
    .timeline__item:nth-child(even) { padding-left:  52%; text-align: left;  }

    .timeline__dot {
        left: 50%; transform: translateX(-50%);
        width: clamp(32px, 4vw, 40px);
        height: clamp(32px, 4vw, 40px);
        font-size: clamp(1rem, 1.5vw, 1.125rem);
        border-width: 4px;
    }

    .timeline__item:nth-child(odd)  .timeline__card { border-right: 4px solid var(--primary-light); border-left: none; }
    .timeline__item:nth-child(even) .timeline__card { border-left:  4px solid var(--primary-light); }

    body.js-reveals .timeline__item.reveal                 { transform: translateX(-22px) translateY(10px); }
    body.js-reveals .timeline__item:nth-child(even).reveal { transform: translateX( 22px) translateY(10px); }
    body.js-reveals .timeline__item.reveal.is-visible      { transform: none; }
}