:root {
  color-scheme: light;
  --bg: #f5f7fb;
  --card: #ffffff;
  --text: #172033;
  --muted: #667085;
  --border: #d0d5dd;
  --primary: #111827;
  --primary-hover: #253047;
  --soft: #eef2f7;
  --success-bg: #ecfdf3;
  --success-text: #027a48;
  --warning-bg: #fffaeb;
  --warning-text: #b54708;
  --error-bg: #fef3f2;
  --error-text: #b42318;
  --shadow: 0 20px 50px rgba(16, 24, 40, 0.10);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family:
    Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP",
    "Hiragino Kaku Gothic ProN", "Yu Gothic", sans-serif;
  background:
    radial-gradient(circle at top left, #eaf0ff 0, transparent 34rem),
    var(--bg);
  color: var(--text);
}

button,
textarea,
input {
  font: inherit;
}

.container {
  width: min(100% - 32px, 760px);
  margin: 0 auto;
  padding: 64px 0;
}

.card {
  background: var(--card);
  border: 1px solid rgba(208, 213, 221, 0.8);
  border-radius: 24px;
  padding: 36px;
  box-shadow: var(--shadow);
}

.badge {
  display: inline-flex;
  align-items: center;
  padding: 7px 11px;
  border-radius: 999px;
  background: var(--soft);
  color: #344054;
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.03em;
}

h1 {
  margin: 18px 0 12px;
  font-size: clamp(2rem, 5vw, 3.2rem);
  line-height: 1.12;
  letter-spacing: -0.04em;
}

.description,
.note,
.message {
  color: var(--muted);
  line-height: 1.75;
}

.description {
  margin: 0 0 28px;
}

code {
  padding: 2px 6px;
  border-radius: 6px;
  background: var(--soft);
  font-size: 0.92em;
}

label {
  display: block;
  margin-bottom: 9px;
  font-weight: 700;
}

textarea,
.result-row input {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: #fff;
  color: var(--text);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

textarea {
  resize: vertical;
  min-height: 122px;
  padding: 14px 16px;
  line-height: 1.55;
}

textarea:focus,
.result-row input:focus {
  outline: none;
  border-color: #667085;
  box-shadow: 0 0 0 4px rgba(102, 112, 133, 0.12);
}

.actions {
  display: flex;
  gap: 12px;
  margin-top: 16px;
}

button {
  border: 0;
  border-radius: 12px;
  padding: 12px 18px;
  cursor: pointer;
  font-weight: 700;
  transition: transform 0.15s ease, background-color 0.15s ease, opacity 0.15s ease;
}

button:hover {
  transform: translateY(-1px);
}

button:active {
  transform: translateY(0);
}

#convert-button,
.copy-button {
  background: var(--primary);
  color: #fff;
}

#convert-button:hover,
.copy-button:hover {
  background: var(--primary-hover);
}

.secondary {
  background: var(--soft);
  color: #344054;
}

.result {
  margin-top: 28px;
  padding: 22px;
  border-radius: 16px;
  background: #f8fafc;
  border: 1px solid #e4e7ec;
}

.hidden {
  display: none;
}

.result-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 12px;
}

.result-header h2 {
  margin: 0;
  font-size: 1.05rem;
}

.status {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 5px 10px;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 700;
}

.status.success {
  background: var(--success-bg);
  color: var(--success-text);
}

.status.warning {
  background: var(--warning-bg);
  color: var(--warning-text);
}

.status.error {
  background: var(--error-bg);
  color: var(--error-text);
}

.result-row {
  display: flex;
  gap: 10px;
}

.result-row input {
  min-width: 0;
  padding: 12px 14px;
}

.copy-button {
  flex: 0 0 auto;
}

.message {
  margin: 12px 0 0;
  font-size: 0.92rem;
}

.note {
  margin: 24px 0 0;
  font-size: 0.82rem;
}

@media (max-width: 600px) {
  .container {
    width: min(100% - 20px, 760px);
    padding: 24px 0;
  }

  .card {
    padding: 24px 18px;
    border-radius: 18px;
  }

  .actions,
  .result-row {
    flex-direction: column;
  }

  button {
    width: 100%;
  }
}