:root {
    --cor-primaria: #4f46e5;
    --cor-texto: #1f2937;
    --cor-texto-suave: #6b7280;
    --cor-borda: #d1d5db;
    --cor-fundo-card: #ffffff;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1.5rem;
    background: linear-gradient(160deg, #eef1fb, #dfe4f5);
    font-family: Arial, Helvetica, sans-serif;
    color: var(--cor-texto);
}

.calculadora {
    width: 100%;
    max-width: 340px;
    background: var(--cor-fundo-card);
    border-radius: 16px;
    padding: 1.75rem 1.5rem;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.12);
}

h1 {
    font-size: 1.15rem;
    text-align: center;
    margin: 0 0 1.5rem;
    font-family: Impact, Haettenschweiler, 'Arial Narrow Bold', sans-serif;
    letter-spacing: 0.5px;
}

.campo {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    margin-bottom: 1rem;
}

.campo label {
    font-size: 0.8rem;
    color: var(--cor-texto-suave);
}

input[type='number'],
#operacao {
    width: 100%;
    padding: 0.7rem 0.8rem;
    border-radius: 8px;
    border: 1px solid var(--cor-borda);
    font-size: 1rem;
    background: #fff;
}

input[type='number']:focus,
#operacao:focus {
    outline: none;
    border-color: var(--cor-primaria);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.15);
}

.resultado {
    margin-top: 1.25rem;
    padding: 1rem;
    border-radius: 10px;
    background: #f4f6fb;
    text-align: center;
}

.resposta {
    margin: 0 0 0.25rem;
    font-size: 0.8rem;
    color: var(--cor-texto-suave);
    font-family: Arial, Helvetica, sans-serif;
    background: transparent;
}

#resposta {
    font-size: 1.6rem;
    font-weight: bold;
    color: var(--cor-texto);
    word-break: break-word;
}

@media (min-width: 480px) {
    .calculadora {
        max-width: 380px;
        padding: 2.25rem 2rem;
    }

    h1 {
        font-size: 1.4rem;
        margin-bottom: 1.75rem;
    }

    #resposta {
        font-size: 1.8rem;
    }
}