/* ── CHALLENGE ── */
.ch-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(210px,1fr));gap:18px;margin-top:50px}
.ch-card{background:var(--card);border-radius:18px;padding:32px 24px;text-align:center;border:1.5px solid var(--border);transition:transform .4s ease,border-color .4s ease,box-shadow .4s ease;position:relative;overflow:hidden}
.ch-card::before{content:'';position:absolute;top:0;left:0;right:0;height:3px;background:linear-gradient(90deg,var(--teal),var(--teal-dark));transform:scaleX(0);transition:transform .4s ease;transform-origin:left}
.ch-card:hover{transform:translateY(-6px);border-color:rgba(44,201,206,.32);box-shadow:0 12px 22px rgba(44,201,206,.12)}
.ch-card:hover::before{transform:scaleX(1)}
.ch-num{font-size:2.9rem;font-weight:900;color:var(--teal-dark);line-height:1}
.ch-unit{font-size:.78rem;font-weight:500;color:var(--text3);margin-bottom:9px}
.ch-title{font-size:.93rem;font-weight:700;color:var(--text);margin-bottom:5px}
.ch-desc{font-size:.81rem;color:var(--text2);line-height:1.62}