```css
/* Reset e stili di base */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Poppins', Arial, sans-serif;
}

body {
  background-color: #f5f7fa;
  color: #333;
  min-height: 100vh;
}

/* Layout Dashboard */
.dashboard {
  display: flex;
  min-height: 100vh;
}

/* Sidebar */
.sidebar {
  width: 250px;
  background: linear-gradient(135deg, #0f2027, #203a43, #2c5364);
  color: #fff;
  padding: 2rem 1rem;
  display: flex;
  flex-direction: column;
  position: sticky;
  top: 0;
  height: 100vh;
  box-shadow: 2px 0 10px rgba(0, 0, 0, 0.1);
}

.sidebar h2 {
  font-size: 1.8rem;
  margin-bottom: 2rem;
  text-align: center;
  letter-spacing: 1px;
  position: relative;
  padding-bottom: 1rem;
}

.sidebar h2:after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 25%;
  width: 50%;
  height: 3px;
  background: linear-gradient(90deg, transparent, #4CAF50, transparent);
}

.sidebar nav {
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
  margin-top: 1rem;
}

.sidebar nav a {
  padding: 0.8rem 1.2rem;
  color: #e0e0e0;
  text-decoration: none;
  border-radius: 8px;
  transition: all 0.3s ease;
  display: flex;
  align-items: center;
  gap: 10px;
}

.sidebar nav a:before {
  font-family: 'Font Awesome 6 Free';
  font-weight: 900;
}

.sidebar nav a:nth-child(1):before { content: '\f015'; } /* Casa */
.sidebar nav a:nth-child(2):before { content: '\f007'; } /* Utente */
.sidebar nav a:nth-child(3):before { content: '\f145'; } /* Biglietto */
.sidebar nav a:nth-child(4):before { content: '\f073'; } /* Calendario */
.sidebar nav a:nth-child(5):before { content: '\f6fc'; } /* Dumbbell */
.sidebar nav a:nth-child(6):before { content: '\f2f5'; } /* Uscita */

.sidebar nav a:hover {
  background-color: rgba(255, 255, 255, 0.1);
  transform: translateX(5px);
}

.sidebar nav a.active {
  background-color: #4CAF50;
  color: white;
  box-shadow: 0 4px 8px rgba(76, 175, 80, 0.3);
}

/* Contenuto principale */
.content {
  flex: 1;
  padding: 2rem;
  overflow-y: auto;
}

.content h1 {
  color: #333;
  margin-bottom: 2rem;
  font-size: 2rem;
  position: relative;
  padding-bottom: 0.5rem;
}

.content h1:after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100px;
  height: 4px;
  background: #4CAF50;
  border-radius: 2px;
}

/* Filtro categorie */
.filtro-container {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 2rem;
  background-color: white;
  padding: 1rem;
  border-radius: 10px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
}

.filtro-container input[type="radio"] {
  display: none;
}

.filtro-container label {
  padding: 0.5rem 1rem;
  border-radius: 20px;
  cursor: pointer;
  font-weight: 500;
  transition: all 0.3s ease;
  border: 2px solid #e0e0e0;
}

.filtro-container label:hover {
  background-color: #f5f5f5;
}

.filtro-container input[type="radio"]:checked + label {
  background-color: #4CAF50;
  color: white;
  border-color: #4CAF50;
  box-shadow: 0 2px 4px rgba(76, 175, 80, 0.3);
}

/* Griglia istruttori */
.istruttori {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 2rem;
}

/* Card istruttore */
.card {
  background-color: white;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.1);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  display: flex;
  flex-direction: column;
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 0 12px 25px rgba(0, 0, 0, 0.15);
}

.card img {
  width: 100%;
  height: 220px;
  object-fit: cover;
  border-bottom: 3px solid #4CAF50;
}

.card h3 {
  padding: 1.2rem 1.5rem 0.5rem;
  font-size: 1.2rem;
  color: #333;
}

.card p {
  padding: 0 1.5rem;
  margin-bottom: 0.5rem;
  color: #666;
  line-height: 1.5;
}

.card p:last-child {
  margin-bottom: 1.5rem;
}

/* Filtro categorie */
#filtro-tutti:checked ~ .istruttori .card {
  display: flex;
}

/* Nascondi tutte le carte quando un filtro è selezionato */
input[name="filtro"]:not(#filtro-tutti):checked ~ .istruttori .card {
  display: none;
}

/* Per ogni categoria, mostra solo le card corrispondenti */
#filtro-yoga:checked ~ .istruttori .categoria-yoga,
#filtro-pilates:checked ~ .istruttori .categoria-pilates,
#filtro-cardiofitness:checked ~ .istruttori .categoria-cardiofitness,
#filtro-funzionale:checked ~ .istruttori .categoria-funzionale,
#filtro-bodybuilding:checked ~ .istruttori .categoria-bodybuilding,
#filtro-crossfit:checked ~ .istruttori .categoria-crossfit,
#filtro-danza:checked ~ .istruttori .categoria-danza,
#filtro-nuoto:checked ~ .istruttori .categoria-nuoto {
  display: flex;
}

/* Responsive */
@media (max-width: 768px) {
  .dashboard {
    flex-direction: column;
  }
  
  .sidebar {
    width: 100%;
    height: auto;
    position: relative;
    padding: 1rem;
  }
  
  .sidebar h2 {
    margin-bottom: 1rem;
  }
  
  .sidebar nav {
    flex-direction: row;
    overflow-x: auto;
    padding-bottom: 0.5rem;
  }
  
  .sidebar nav a {
    white-space: nowrap;
  }
  
  .content {
    padding: 1rem;
  }
  
  .istruttori {
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 1rem;
  }
}

/* Animazioni */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

.card {
  animation: fadeIn 0.5s ease-in-out;
}

.istruttori .card:nth-child(2) { animation-delay: 0.1s; }
.istruttori .card:nth-child(3) { animation-delay: 0.2s; }
.istruttori .card:nth-child(4) { animation-delay: 0.3s; }
.istruttori .card:nth-child(5) { animation-delay: 0.4s; }
.istruttori .card:nth-child(6) { animation-delay: 0.5s; }
.istruttori .card:nth-child(7) { animation-delay: 0.6s; }