:root {
  --main-blue: #48b9e6;
  --main-bg: #e6edef;
  --main-white: #fff;
  --main-shadow: 0 2px 8px rgba(33, 33, 33, 0.18);
  --main-radius: 12px;
  --main-gray: #b0b0b0;
  --main-dark: #222;
}
body {
  background: var(--main-bg);
  margin: 0;
  font-family: 'Roboto', 'Segoe UI', 'Meiryo', sans-serif;
}
.main-header {
  background: var(--main-blue);
  color: var(--main-white);
  padding: 28px 0 14px 0;
  text-align: center;
  margin-bottom: 32px;
  box-shadow: var(--main-shadow);
}
.main-header h2 {
  margin: 0;
  font-size: 2.2em;
  letter-spacing: 0.1em;
  color: var(--main-white);
  font-style: italic;
  font-weight: bold;
  text-align: left;
  padding-left: 24px;
}
.main-header .powered {
  margin: 6px 0 0 0;
  font-size: 1em;
  color: var(--main-white);
  letter-spacing: 0.08em;
  text-align: left;
  padding-left: 24px;
}
.container {
  max-width: 800px;
  margin: 40px auto;
  padding: 32px 32px 24px 32px;
  background: var(--main-white);
  border-radius: var(--main-radius);
  box-shadow: var(--main-shadow);
  text-align: center;
  display: flex;
  flex-direction: column;
  gap: 18px;
}
.input-group {
  margin-bottom: 18px;
  text-align: left;
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.input-group label {
  font-weight: 500;
  color: var(--main-dark);
}
.input-group input[type="file"],
.input-group input[type="number"] {
  width: 100%;
  padding: 10px 12px;
  border: 1.5px solid #cfd8dc;
  border-radius: 6px;
  font-size: 1em;
  background: #f5f7fa;
  transition: border 0.2s;
  outline: none;
}
.input-group input[type="number"]:focus,
.input-group input[type="file"]:focus {
  border: 1.5px solid var(--main-blue);
}
.button-grid {
  display: flex;
  flex-direction: row;
  gap: 8px;
  margin-top: 20px;
  justify-content: center;
  flex-wrap: nowrap;
  overflow-x: auto;
}
.square-btn {
  min-width: 44px;
  max-width: 44px;
  min-height: 44px;
  max-height: 44px;
  font-size: 1em;
  padding: 0;
  border-radius: 8px;
  font-weight: bold;
  border: none;
  cursor: pointer;
  transition: background 0.2s, color 0.2s, box-shadow 0.2s;
  box-shadow: 0 1px 3px rgba(33,33,33,0.10);
  outline: none;
  margin-bottom: 2px;
}
.square-btn.fixed-gray {
  background: var(--main-gray);
  color: #fff;
  cursor: default;
  box-shadow: none;
}
.square-btn.toggle-gray {
  background: #f5f7fa;
  color: #333;
  border: 1.5px solid #cfd8dc;
}
.square-btn.toggle-blue {
  background: var(--main-blue);
  color: #fff;
  border: 1.5px solid var(--main-blue);
  box-shadow: 0 2px 6px rgba(72,185,230,0.18);
}
.square-btn:active {
  box-shadow: 0 1px 1px rgba(33,33,33,0.10);
}
.generate-btn {
  display: block;
  width: 100%;
  margin: 16px 0 20px 0;
  padding: 14px 0;
  background: var(--main-blue);
  color: #fff;
  font-size: 1.1em;
  font-weight: bold;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  box-shadow: 0 2px 6px rgba(72,185,230,0.18);
  transition: background 0.2s, box-shadow 0.2s;
  letter-spacing: 0.04em;
}
.generate-btn:hover {
  background: #2699c7;
  box-shadow: 0 4px 12px rgba(72,185,230,0.22);
}
.synth-section {
  background: #f5f7fa;
  border-radius: var(--main-radius);
  box-shadow: 0 1px 4px rgba(33,33,33,0.08);
  padding: 18px 18px 10px 18px;
  margin-bottom: 10px;
  margin-top: 24px;
  text-align: left;
}
.synth-section label {
  font-weight: 500;
  color: var(--main-dark);
}
#mix-ratio {
  accent-color: var(--main-blue);
  height: 4px;
  border-radius: 2px;
  background: #cfd8dc;
  margin-top: 8px;
}
#mix-ratio::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--main-blue);
  box-shadow: 0 2px 6px rgba(72,185,230,0.18);
  border: 2px solid #fff;
  cursor: pointer;
  transition: background 0.2s;
}
#mix-ratio:focus {
  outline: none;
}
#mix-ratio::-moz-range-thumb {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--main-blue);
  box-shadow: 0 2px 6px rgba(72,185,230,0.18);
  border: 2px solid #fff;
  cursor: pointer;
  transition: background 0.2s;
}
#mix-ratio::-ms-thumb {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--main-blue);
  box-shadow: 0 2px 6px rgba(72,185,230,0.18);
  border: 2px solid #fff;
  cursor: pointer;
  transition: background 0.2s;
}
#mix-ratio::-webkit-slider-runnable-track {
  height: 4px;
  border-radius: 2px;
  background: #cfd8dc;
}
#mix-ratio::-ms-fill-lower {
  background: #cfd8dc;
}
#mix-ratio::-ms-fill-upper {
  background: #cfd8dc;
}
#mix-ratio:focus::-webkit-slider-thumb {
  background: #2699c7;
}
#mix-ratio:focus::-moz-range-thumb {
  background: #2699c7;
}
#mix-ratio:focus::-ms-thumb {
  background: #2699c7;
}
#mix-ratio-value {
  font-weight: bold;
  color: var(--main-blue);
  margin-left: 4px;
}
audio {
  border-radius: 8px;
  box-shadow: 0 1px 4px rgba(33,33,33,0.10);
  background: #f5f7fa;
  padding: 4px 0;
}