/* ───── Tarjeta de estudio ───── */
.umbral-fc-card{
    border:1px solid #e5e7eb;
    border-radius:8px;
    padding:40px 28px;
    text-align:center;
    background:#fff;
    box-shadow:0 4px 8px rgba(0,0,0,.05);
}
.umbral-fc-front{font-size:1.35rem;font-weight:600;}
.umbral-fc-back {display:none;font-size:1.1rem;margin-top:22px;}
.umbral-fc-card.show-back .umbral-fc-back{display:block;}

.umbral-fc-buttons{margin-top:30px;display:flex;justify-content:space-around}
.umbral-fc-btn{
    background:#3b82f6;color:#fff;border:none;
    padding:8px 14px;border-radius:20px;cursor:pointer;font-size:.9rem;
    transition:.15s background;
}
.umbral-fc-btn:hover{background:#2563eb}

/* ───── Tablero de decks ───── */
.umbral-fc-deck-grid{
    display:grid;
    gap:24px;
    grid-template-columns:repeat(auto-fill,minmax(180px,1fr));
}

.umbral-fc-deck-card{
    display:flex;
    align-items:center;
    justify-content:center;
    background:#f9fafb;           /* gris muy claro */
    border:1px solid #e5e7eb;
    border-radius:10px;           /* radio 10 px */
    padding:36px 20px;
    text-decoration:none;
    color:#111827;
    box-shadow:0 2px 4px rgba(0,0,0,.04);
    transition:.25s transform,.25s box-shadow;
}
.umbral-fc-deck-card:hover{
    transform:translateY(-6px) scale(1.03);
    box-shadow:0 10px 16px rgba(0,0,0,.08);
}