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

body {
    font-family: Arial, sans-serif;
    background: #f2f4f8;
    display: flex;
    justify-content: center;
    min-height: 100vh;
    padding: 2rem;
}

.tarjeta {
    background: #ffffff;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    padding: 2rem;
    width: 100%;
    max-width: 640px;
    align-self: flex-start;
}

h1 {
    margin-bottom: 1rem;
    color: #1a1a2e;
}

.fila {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.fila input,
.fila select,
.fila button {
    padding: 0.5rem;
    font-size: 1rem;
    border: 1px solid #cbd5e0;
    border-radius: 4px;
}

.fila input {
    flex: 1;
    min-width: 100px;
}

.fila button {
    background: #2563eb;
    color: #fff;
    border: none;
    cursor: pointer;
}

.fila button:hover {
    background: #1d4ed8;
}

.resultado {
    margin-top: 1.5rem;
    font-size: 1.25rem;
    font-weight: bold;
    color: #1a1a2e;
}

.mensaje {
    margin-top: 0.5rem;
    color: #b91c1c;
}

.mensaje.aviso {
    color: #92400e;
}

h2 {
    margin-top: 2rem;
    margin-bottom: 0.5rem;
    color: #1a1a2e;
}

#historial {
    list-style: none;
}

#historial li {
    padding: 0.5rem 0;
    border-bottom: 1px solid #e2e8f0;
    font-family: monospace;
}

#historial li .fecha {
    color: #64748b;
    font-size: 0.8rem;
}