body {
    font-family: Arial, sans-serif;
    background-color: #f4f4f9;
    color: #333;
    padding: 20px;
    margin: 0;
}

h1 {
    color: #2c3e50;
    border-bottom: 2px solid #2c3e50;
    padding-bottom: 10px;
}

.ejercicio {
    background-color: white;
    border-radius: 8px;
    padding: 20px;
    margin-bottom: 25px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

/* La tarjeta azul que querías */
.explicacion {
    background-color: #ebf8ff;
    border-left: 4px solid #3182ce;
    color: #2b6cb0;
    padding: 15px;
    margin-bottom: 20px;
    border-radius: 0 6px 6px 0;
    font-size: 0.95rem;
}

.formulario {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
    align-items: center;
    margin-bottom: 15px;
}

button {
    padding: 7px 15px;
    background-color: #3182ce;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
}

.resultado {
    background-color: #e6fffa;
    border: 1px solid #b2f5ea;
    color: #234e52;
    padding: 10px;
    border-radius: 4px;
    font-weight: bold;
}

.estilo {
    background-color: #3182ce;
    width: 85%;
    margin: 20px auto;
    padding: 20px;
    border-radius: 8px;
}

.flex {
    display: flex;
    justify-content: space-around;
}

.fondo {
    background-color: white;
    text-align: center;
    width: 120px;
    padding: 10px;
    border-radius: 4px;
}

.fondo img {
    cursor: pointer;
    height: 120px;
}