* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: #f4f4f4;
  color: #111;
  font-family: Arial, sans-serif;
  display: grid;
  place-items: center;
  padding: 24px;
}

.app {
  width: min(520px, 100%);
  background: #fff;
  border: 1px solid #111;
  padding: 22px;
}

h1 {
  margin: 0;
  font-size: 24px;
}

.hint {
  margin: 10px 0 18px;
  font-size: 14px;
}

.frequency {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: 8px;
  font-size: 16px;
}

#frequency {
  width: 100%;
  margin: 0 0 12px;
}

.custom-frequency {
  display: grid;
  gap: 8px;
  margin: 0 0 18px;
  font-size: 14px;
}

#custom-frequency {
  width: 100%;
  border: 1px solid #111;
  padding: 8px 10px;
  font-size: 14px;
}

.waveforms {
  margin: 0;
  padding: 12px;
  border: 1px solid #111;
  display: grid;
  gap: 10px;
}

.waveforms legend {
  padding: 0 6px;
}

.waveforms label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

.toggle {
  margin-top: 16px;
  border: 1px solid #111;
  background: #fff;
  color: #111;
  padding: 8px 12px;
  font-size: 14px;
  cursor: pointer;
}

.toggle:hover,
.toggle:focus-visible {
  background: #111;
  color: #fff;
}

.back {
  display: inline-block;
  margin-top: 18px;
  color: #111;
  text-decoration: none;
  border: 1px solid #111;
  padding: 8px 12px;
  font-size: 14px;
}

.back:hover,
.back:focus-visible {
  background: #111;
  color: #fff;
}