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

body {
    background: #111;
    font-family: Arial, sans-serif;
}

/* Contenedor principal */
.app {
    height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 30px;
}

/* Semáforo */
.semaforo {
    background: #222;
    padding: 20px;
    border-radius: 25px;
    width: 120px;
}

/* Luces */
.luz {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    background: #333;
    margin: 15px auto;
    transition: all 0.3s ease;
}

/* Estados */
.activo.rojo {
    background: red;
    box-shadow: 0 0 25px red;
}

.activo.amarillo {
    background: yellow;
    box-shadow: 0 0 25px yellow;
}

.activo.verde {
    background: lime;
    box-shadow: 0 0 25px lime;
}

/* Botón táctil */
button {
    width: 80%;
    max-width: 300px;
    padding: 18px;
    font-size: 20px;
    border: none;
    border-radius: 15px;
    background: #4CAF50;
    color: white;
    cursor: pointer;
}

/* Efecto al tocar */
button:active {
    transform: scale(0.95);
}