:root {
  --bg: #0f172a;
  --bg-soft: #111827;
  --card: #1f2937;
  --text: #e5e7eb;
  --muted: #9ca3af;
  --accent: #f59e0b;
  --accent-2: #22d3ee;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", "Hiragino Kaku Gothic ProN", "Meiryo", sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 20% 15%, #1e3a8a 0%, transparent 28%),
    radial-gradient(circle at 80% 80%, #312e81 0%, transparent 35%),
    linear-gradient(145deg, var(--bg), var(--bg-soft));
  min-height: 100vh;
}

.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 24px;
  display: grid;
  gap: 18px;
}

header h1 {
  margin: 0;
  font-size: 2rem;
  letter-spacing: 0.03em;
}

header p {
  margin: 8px 0 0;
  color: var(--muted);
}

.card {
  background: color-mix(in oklab, var(--card) 88%, black);
  border: 1px solid #374151;
  border-radius: 14px;
  padding: 16px;
  box-shadow: 0 16px 40px rgba(0, 0, 0, 0.25);
}

h2 {
  margin-top: 0;
}

label {
  display: grid;
  gap: 6px;
  font-size: 0.95rem;
}

textarea,
input,
select,
button {
  font: inherit;
}

textarea,
input[type="file"],
select {
  width: 100%;
  border-radius: 10px;
  border: 1px solid #4b5563;
  padding: 10px;
  background: #111827;
  color: var(--text);
}

textarea {
  resize: vertical;
}

.actions {
  margin-top: 14px;
  margin-bottom: 14px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

button {
  border: none;
  border-radius: 10px;
  padding: 10px 14px;
  background: linear-gradient(135deg, var(--accent), #ef4444);
  color: #111827;
  font-weight: 700;
  cursor: pointer;
}

button:nth-child(2),
button:nth-child(3),
button:nth-child(4),
#decodeBtn {
  background: linear-gradient(135deg, var(--accent-2), #38bdf8);
}

button:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

#status {
  margin-top: 12px;
  color: var(--muted);
}

canvas {
  width: 100%;
  height: auto;
  border: 1px solid #374151;
  border-radius: 10px;
  background: #0b1220;
}

audio {
  width: 100%;
  margin-top: 12px;
}