*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

    :root {
      --bg: #f0f4ff;
      --card: #ffffff;
      --text: #12172b;
      --muted: #8a93a8;
      --border: #e8ecf4;
      --radius: 20px;
    }

    body {
      font-family: 'Nunito', sans-serif;
      background: var(--bg);
      color: var(--text);
      min-height: 100vh;
    }

    /* ── HERO ── */
    .hero {
      background: linear-gradient(135deg, #1a1f4e 0%, #2d3580 50%, #1e4799 100%);
      padding: 6rem 1.5rem 5rem;
      text-align: center;
      position: relative;
      overflow: hidden;
    }
    .hero::before {
      content: '';
      position: absolute;
      inset: 0;
      background: radial-gradient(ellipse at 70% 30%, rgba(255,200,80,0.12) 0%, transparent 60%),
                  radial-gradient(ellipse at 20% 80%, rgba(100,180,255,0.12) 0%, transparent 50%);
    }
    .hero-badge {
      display: inline-flex;
      align-items: center;
      gap: 7px;
      background: rgba(255,255,255,0.12);
      border: 1px solid rgba(255,255,255,0.22);
      color: rgba(255,255,255,0.85);
      font-size: 12px;
      font-weight: 700;
      letter-spacing: 1.5px;
      text-transform: uppercase;
      padding: 6px 16px;
      border-radius: 30px;
      margin-bottom: 1.2rem;
      position: relative;
    }
    .hero h1 {
      font-size: clamp(28px, 5vw, 48px);
      font-weight: 900;
      color: #fff;
      line-height: 1.15;
      margin-bottom: 0.75rem;
      position: relative;
    }
    .hero h1 span { color: #ffd166; }
    .hero p {
      font-size: 16px;
      color: rgba(255,255,255,0.7);
      max-width: 520px;
      margin: 0 auto 1.8rem;
      line-height: 1.6;
      position: relative;
    }
    .hero-stats {
      display: inline-flex;
      gap: 2rem;
      background: rgba(255,255,255,0.1);
      border: 1px solid rgba(255,255,255,0.18);
      border-radius: 16px;
      padding: 0.9rem 2rem;
      position: relative;
    }
    .stat { text-align: center; }
    .stat-num { font-size: 24px; font-weight: 800; color: #fff; line-height: 1; }
    .stat-lbl { font-size: 11px; color: rgba(255,255,255,0.6); font-weight: 600; margin-top: 3px; text-transform: uppercase; letter-spacing: 0.8px; }

    /* ── FILTER BAR ── */
    .filter-wrap {
      max-width: 1080px;
      margin: -28px auto 0;
      padding: 0 1.5rem;
      position: relative;
      z-index: 10;
    }
    .filter-bar {
      background: #fff;
      border-radius: 16px;
      box-shadow: 0 8px 32px rgba(0,0,0,0.10);
      padding: 1rem 1.25rem;
      display: flex;
      align-items: center;
      gap: 0.6rem;
      flex-wrap: wrap;
    }
    .filter-label { font-size: 12px; font-weight: 700; color: var(--muted); text-transform: uppercase; letter-spacing: 1px; margin-right: 4px; flex-shrink: 0; }
    .filter-btn {
      padding: 6px 16px;
      border-radius: 30px;
      border: 1.5px solid var(--border);
      background: transparent;
      font-family: 'Nunito', sans-serif;
      font-size: 13px;
      font-weight: 700;
      color: var(--muted);
      cursor: pointer;
      transition: all 0.18s;
    }
    .filter-btn:hover { border-color: #4a6cf7; color: #4a6cf7; }
    .filter-btn.active { background: #4a6cf7; border-color: #4a6cf7; color: #fff; }

    /* ── MAIN GRID ── */
    .main-wrap { max-width: 1080px; margin: 2.5rem auto; padding: 0 1.5rem 4rem; }

    .exp-grid {
      display: grid;
      grid-template-columns: repeat(auto-fill, minmax(310px, 1fr));
      gap: 1.6rem;
    }

    /* ── CARD ── */
    .exp-card {
      background: var(--card);
      border-radius: var(--radius);
      overflow: hidden;
      box-shadow: 0 2px 12px rgba(0,0,0,0.06);
      border: 1px solid var(--border);
      display: flex;
      flex-direction: column;
      transition: transform 0.22s ease, box-shadow 0.22s ease;
    }
    .exp-card:hover {
      transform: translateY(-5px);
      box-shadow: 0 12px 36px rgba(0,0,0,0.12);
    }
    .exp-card.hidden { display: none; }

    /* Banner */
    .card-banner {
      position: relative;
      height: 190px;
      overflow: hidden;
      flex-shrink: 0;
    }
    .card-banner img {
      width: 100%; height: 100%;
      object-fit: cover;
      display: block;
      transition: transform 0.4s ease;
    }
    .exp-card:hover .card-banner img { transform: scale(1.04); }
    .banner-overlay {
      position: absolute;
      inset: 0;
      display: flex;
      align-items: flex-end;
      justify-content: space-between;
      padding: 0.9rem 1.1rem;
    }
    .exp-num-badge {
      font-family: 'Caveat', cursive;
      font-size: 48px;
      font-weight: 700;
      color: rgba(255,255,255,0.92);
      line-height: 1;
      text-shadow: 0 2px 8px rgba(0,0,0,0.25);
    }
    .exp-emoji { font-size: 38px; line-height: 1; filter: drop-shadow(0 2px 6px rgba(0,0,0,0.3)); }

    /* Concept tag on banner */
    .concept-tag {
      position: absolute;
      top: 12px;
      left: 12px;
      font-size: 10px;
      font-weight: 800;
      text-transform: uppercase;
      letter-spacing: 1.2px;
      padding: 4px 11px;
      border-radius: 20px;
      backdrop-filter: blur(8px);
      -webkit-backdrop-filter: blur(8px);
    }

    /* Colour themes — one per card */
    /* blue */ .t-blue .card-banner { background: #9ec5f5; }
    .t-blue .banner-overlay { background: linear-gradient(to top, rgba(15,60,130,0.65) 0%, transparent 65%); }
    .t-blue .concept-tag { background: rgba(30,100,210,0.75); color: #deeeff; }
    .t-blue .step-num { background: #deeeff; color: #1450a3; }
    .t-blue .obs-box { background: #e8f2ff; color: #1450a3; }
    .t-blue .science-box { border-color: #378add; }
    .t-blue .outcome-dot { background: #378add; }
    .t-blue .related-link { color: #1450a3; border-color: #b5d4f4; background: #f0f7ff; }
    .t-blue .related-link:hover { background: #dceefb; }
    .t-blue .card-footer { border-top-color: #deeeff; }
    .t-blue .diff-badge { background: #deeeff; color: #1450a3; }

    /* pink */ .t-pink .card-banner { background: #f2b3cc; }
    .t-pink .banner-overlay { background: linear-gradient(to top, rgba(110,20,60,0.65) 0%, transparent 65%); }
    .t-pink .concept-tag { background: rgba(170,40,90,0.75); color: #ffe8f2; }
    .t-pink .step-num { background: #ffe8f2; color: #a0284f; }
    .t-pink .obs-box { background: #fff0f5; color: #a0284f; }
    .t-pink .science-box { border-color: #d4537e; }
    .t-pink .outcome-dot { background: #d4537e; }
    .t-pink .related-link { color: #a0284f; border-color: #f4c0d1; background: #fff5f8; }
    .t-pink .related-link:hover { background: #fde8ef; }
    .t-pink .diff-badge { background: #ffe8f2; color: #a0284f; }

    /* green */ .t-green .card-banner { background: #a8dbb8; }
    .t-green .banner-overlay { background: linear-gradient(to top, rgba(10,80,40,0.65) 0%, transparent 65%); }
    .t-green .concept-tag { background: rgba(20,110,55,0.75); color: #d8f5e4; }
    .t-green .step-num { background: #d8f5e4; color: #1a6e3a; }
    .t-green .obs-box { background: #eaf8ef; color: #1a6e3a; }
    .t-green .science-box { border-color: #3ab869; }
    .t-green .outcome-dot { background: #3ab869; }
    .t-green .related-link { color: #1a6e3a; border-color: #a8dbb8; background: #f0faf4; }
    .t-green .related-link:hover { background: #d8f5e4; }
    .t-green .diff-badge { background: #d8f5e4; color: #1a6e3a; }

    /* amber */ .t-amber .card-banner { background: #f5d08a; }
    .t-amber .banner-overlay { background: linear-gradient(to top, rgba(100,55,0,0.65) 0%, transparent 65%); }
    .t-amber .concept-tag { background: rgba(160,90,10,0.75); color: #fff3d4; }
    .t-amber .step-num { background: #fff3d4; color: #a05a0a; }
    .t-amber .obs-box { background: #fff8e6; color: #a05a0a; }
    .t-amber .science-box { border-color: #e6a817; }
    .t-amber .outcome-dot { background: #e6a817; }
    .t-amber .related-link { color: #a05a0a; border-color: #f5d08a; background: #fffbf0; }
    .t-amber .related-link:hover { background: #fff3d4; }
    .t-amber .diff-badge { background: #fff3d4; color: #a05a0a; }

    /* red */ .t-red .card-banner { background: #f5a5a5; }
    .t-red .banner-overlay { background: linear-gradient(to top, rgba(110,15,15,0.65) 0%, transparent 65%); }
    .t-red .concept-tag { background: rgba(170,30,30,0.75); color: #ffe8e8; }
    .t-red .step-num { background: #ffe8e8; color: #a82020; }
    .t-red .obs-box { background: #fff0f0; color: #a82020; }
    .t-red .science-box { border-color: #e04040; }
    .t-red .outcome-dot { background: #e04040; }
    .t-red .related-link { color: #a82020; border-color: #f5a5a5; background: #fff5f5; }
    .t-red .related-link:hover { background: #ffe8e8; }
    .t-red .diff-badge { background: #ffe8e8; color: #a82020; }

    /* purple */ .t-purple .card-banner { background: #c4b3f2; }
    .t-purple .banner-overlay { background: linear-gradient(to top, rgba(50,20,110,0.65) 0%, transparent 65%); }
    .t-purple .concept-tag { background: rgba(80,40,170,0.75); color: #ede8ff; }
    .t-purple .step-num { background: #ede8ff; color: #5028b0; }
    .t-purple .obs-box { background: #f4f0ff; color: #5028b0; }
    .t-purple .science-box { border-color: #7c55dd; }
    .t-purple .outcome-dot { background: #7c55dd; }
    .t-purple .related-link { color: #5028b0; border-color: #c4b3f2; background: #f8f5ff; }
    .t-purple .related-link:hover { background: #ede8ff; }
    .t-purple .diff-badge { background: #ede8ff; color: #5028b0; }

    /* teal */ .t-teal .card-banner { background: #8fd5d0; }
    .t-teal .banner-overlay { background: linear-gradient(to top, rgba(10,70,70,0.65) 0%, transparent 65%); }
    .t-teal .concept-tag { background: rgba(15,100,100,0.75); color: #d4f5f3; }
    .t-teal .step-num { background: #d4f5f3; color: #0e6e6e; }
    .t-teal .obs-box { background: #e8f9f8; color: #0e6e6e; }
    .t-teal .science-box { border-color: #1dada8; }
    .t-teal .outcome-dot { background: #1dada8; }
    .t-teal .related-link { color: #0e6e6e; border-color: #8fd5d0; background: #f0fbfb; }
    .t-teal .related-link:hover { background: #d4f5f3; }
    .t-teal .diff-badge { background: #d4f5f3; color: #0e6e6e; }

    /* orange */ .t-orange .card-banner { background: #f5b88a; }
    .t-orange .banner-overlay { background: linear-gradient(to top, rgba(110,45,5,0.65) 0%, transparent 65%); }
    .t-orange .concept-tag { background: rgba(175,70,10,0.75); color: #fff0e2; }
    .t-orange .step-num { background: #fff0e2; color: #b54a0a; }
    .t-orange .obs-box { background: #fff6ee; color: #b54a0a; }
    .t-orange .science-box { border-color: #e0782a; }
    .t-orange .outcome-dot { background: #e0782a; }
    .t-orange .related-link { color: #b54a0a; border-color: #f5b88a; background: #fffaf5; }
    .t-orange .related-link:hover { background: #fff0e2; }
    .t-orange .diff-badge { background: #fff0e2; color: #b54a0a; }

    /* indigo */ .t-indigo .card-banner { background: #aab4f0; }
    .t-indigo .banner-overlay { background: linear-gradient(to top, rgba(20,25,100,0.65) 0%, transparent 65%); }
    .t-indigo .concept-tag { background: rgba(45,55,180,0.75); color: #e6e9ff; }
    .t-indigo .step-num { background: #e6e9ff; color: #2d37b4; }
    .t-indigo .obs-box { background: #eef0ff; color: #2d37b4; }
    .t-indigo .science-box { border-color: #4a5ae0; }
    .t-indigo .outcome-dot { background: #4a5ae0; }
    .t-indigo .related-link { color: #2d37b4; border-color: #aab4f0; background: #f5f6ff; }
    .t-indigo .related-link:hover { background: #e6e9ff; }
    .t-indigo .diff-badge { background: #e6e9ff; color: #2d37b4; }

    /* cyan */ .t-cyan .card-banner { background: #90cce8; }
    .t-cyan .banner-overlay { background: linear-gradient(to top, rgba(5,55,90,0.65) 0%, transparent 65%); }
    .t-cyan .concept-tag { background: rgba(10,90,140,0.75); color: #d8f0fa; }
    .t-cyan .step-num { background: #d8f0fa; color: #0a5a8c; }
    .t-cyan .obs-box { background: #e8f6fc; color: #0a5a8c; }
    .t-cyan .science-box { border-color: #12a0d8; }
    .t-cyan .outcome-dot { background: #12a0d8; }
    .t-cyan .related-link { color: #0a5a8c; border-color: #90cce8; background: #f0f8fd; }
    .t-cyan .related-link:hover { background: #d8f0fa; }
    .t-cyan .diff-badge { background: #d8f0fa; color: #0a5a8c; }

    /* ── CARD BODY ── */
    .card-body { padding: 1.25rem 1.25rem 0; flex: 1; display: flex; flex-direction: column; }

    .card-top { display: flex; align-items: flex-start; justify-content: space-between; gap: 8px; margin-bottom: 0.9rem; }
    .exp-title { font-size: 19px; font-weight: 800; line-height: 1.25; color: var(--text); flex: 1; }
    .diff-badge { font-size: 10px; font-weight: 800; padding: 3px 10px; border-radius: 20px; white-space: nowrap; flex-shrink: 0; text-transform: uppercase; letter-spacing: 0.8px; }

    .section-label {
      font-size: 10px; font-weight: 800; text-transform: uppercase;
      letter-spacing: 1.4px; color: var(--muted); margin-bottom: 7px; margin-top: 1rem;
    }

    .materials-list { display: flex; flex-wrap: wrap; gap: 5px; }
    .material-tag {
      font-size: 12px; font-weight: 600; padding: 4px 11px;
      border-radius: 30px; border: 1px solid var(--border);
      color: #555; background: #f7f8fc;
    }

    /* Accordion sections */
    .accordion { border: 1px solid var(--border); border-radius: 12px; overflow: hidden; margin-top: 1rem; }
    .acc-item { border-bottom: 1px solid var(--border); }
    .acc-item:last-child { border-bottom: none; }
    .acc-header {
      display: flex; align-items: center; justify-content: space-between;
      padding: 10px 14px; cursor: pointer;
      font-size: 12px; font-weight: 800; text-transform: uppercase;
      letter-spacing: 1px; color: var(--muted);
      background: #fafbff; user-select: none;
      transition: background 0.15s;
    }
    .acc-header:hover { background: #f2f4fc; }
    .acc-arrow { font-size: 10px; transition: transform 0.25s; }
    .acc-body { display: none; padding: 10px 14px 14px; }
    .acc-item.open .acc-body { display: block; }
    .acc-item.open .acc-arrow { transform: rotate(180deg); }

    .steps-list { list-style: none; }
    .steps-list li {
      display: flex; gap: 10px; align-items: flex-start;
      font-size: 13px; line-height: 1.55; padding: 6px 0;
      border-bottom: 1px solid #f2f2f2; color: #333;
    }
    .steps-list li:last-child { border-bottom: none; }
    .step-num {
      min-width: 23px; height: 23px; border-radius: 50%;
      display: flex; align-items: center; justify-content: center;
      font-size: 11px; font-weight: 800; flex-shrink: 0; margin-top: 1px;
    }

    .obs-box {
      border-radius: 10px; padding: 10px 13px;
      font-size: 13px; line-height: 1.6; font-style: italic;
    }

    .science-box {
      border-left: 3px solid; padding: 9px 12px;
      font-size: 13px; line-height: 1.6;
      background: #f8f9fc; border-radius: 0 8px 8px 0; color: #333;
    }

    .outcomes-list { display: flex; flex-direction: column; gap: 6px; }
    .outcome-item { display: flex; align-items: flex-start; gap: 9px; font-size: 13px; line-height: 1.5; color: #333; }
    .outcome-dot { width: 7px; height: 7px; border-radius: 50%; flex-shrink: 0; margin-top: 5px; }

    /* Related links */
    .related-links { display: flex; flex-direction: column; gap: 6px; margin-top: 0.3rem; }
    .related-link {
      display: flex; align-items: center; gap: 8px;
      text-decoration: none; font-size: 12.5px; font-weight: 700;
      padding: 8px 12px; border-radius: 10px; border: 1px solid;
      transition: background 0.15s, transform 0.15s;
    }
    .related-link:hover { transform: translateX(4px); }
    .related-link-arrow { margin-left: auto; font-size: 12px; opacity: 0.4; }

    /* Card footer */
    .card-footer {
      display: flex; justify-content: space-between; align-items: center;
      padding: 0.75rem 1.25rem; margin-top: 1.1rem;
      border-top: 1px solid var(--border);
      background: #fafbff; font-size: 11.5px; color: var(--muted); font-weight: 700;
    }

    /* ── RESPONSIVE ── */
    @media (max-width: 600px) {
      .hero { padding: 2.5rem 1rem 4rem; }
      .hero-stats { gap: 1.2rem; padding: 0.75rem 1.2rem; }
      .filter-bar { gap: 0.4rem; }
      .exp-grid { grid-template-columns: 1fr; }
    }