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

body {
    font-family: Arial, Helvetica, sans-serif;
    background-color: aliceblue;
}

main {
    padding: 8px 12px;
}

.chart-box {
    height: 356px;
    background-color: white;
    border: 1px solid silver;
    border-radius: 6px;
    padding: 6px;
}

.controls {
    margin-top: 10px;
    display: flex;
    align-items: center;
    gap: 14px;
    background-color: white;
    border: 1px solid silver;
    border-radius: 6px;
    padding: 10px 12px;
}

.controls label {
    font-size: 15px;
    white-space: nowrap;
}

.controls strong {
    color: #c62828;
}

#sigFreq {
    flex: 1;
    min-width: 100px;
}

@media (max-width: 560px) {
    .controls { flex-direction: column; align-items: stretch; gap: 6px; }
    .controls label { white-space: normal; }
}