/* --- STYLES GENERAUX --- */
body {
  font-family: 'Arial', sans-serif;
  margin: 0;
  padding: 0;
  background-color: #f0f2f5; 
  text-align: center;
}

/* --- HEADER --- */
header {
  background-color: #2c3e50; 
  color: white;
  padding: 15px 0;
  box-shadow: 0 2px 5px rgba(0,0,0,0.2);
}

.header-container {
  display: flex;
  justify-content: space-around;
  align-items: center;
}

.logo {
  font-weight: bold;
  font-size: 1.1rem;
  text-transform: uppercase;
}

/* --- CONTENEUR PRINCIPAL --- */
main {
  max-width: 500px;
  margin: 20px auto;
  background: white;
  padding: 25px;
  border-radius: 12px;
  box-shadow: 0 4px 10px rgba(0,0,0,0.1);
}

#instruction {
  background: #e1f5fe; 
  padding: 12px;
  border-radius: 8px;
  color: #0277bd;
  margin-bottom: 25px;
}

/* --- OPERATEURS (DRAGGABLES) --- */
#operations {
  display: flex;
  justify-content: center;
  gap: 15px;
  margin-bottom: 30px;
}

.op {
  width: 55px;
  height: 55px;
  background-color: #fff9c4; 
  border: 2px solid #fbc02d;
  border-radius: 10px;
  line-height: 55px;
  font-size: 24px;
  font-weight: bold;
  cursor: grab; /* Indique qu'on peut attraper l'element */
  z-index: 100; /* Assure que le signe passe par-dessus les equations */
}

/* --- EQUATIONS (DROPZONES) --- */
.dropzone {
  width: 280px;
  height: 55px;
  margin: 10px auto;
  border: 2px dashed #b0bec5; /* Bordure pointillee pour suggerer un vide */
  border-radius: 10px;
  line-height: 55px;
  font-size: 20px;
  background-color: #fafafa;
  transition: all 0.3s ease;
}

/* --- ETATS DE FEEDBACK (COULEURS) --- */
.correct {
  background-color: #c8e6c9 !important; 
  border: 2px solid #4caf50 !important;
  color: #2e7d32;
}

.error {
  background-color: #ffcdd2 !important; 
  border: 2px solid #e53935 !important;
}

/* --- FOOTER --- */
footer {
  margin-top: 40px;
  padding: 20px;
  font-size: 0.85em;
  color: #78909c;
}

/* --- MESSAGE DE REUSSITE --- */
#message-final {
  display: none; /* Cache par defaut via CSS */
  margin-top: 20px;
  padding: 15px;
  border-radius: 10px;
  background-color: #e8f5e9;
  border: 1px solid #2e7d32;
  color: #2e7d32;
  font-weight: bold;
}