:root {
  --bg: #f7f9fb;
  --text: #0b1b2b;
  --muted: #5e6a78;
  --primary: #2ab66f;
  --primary-dark: #229a5c;
  --border: #d9e1ea;
  --card: #ffffff;
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: Inter, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", "Apple Color Emoji", "Segoe UI Emoji";
  color: var(--text);
  background: var(--bg);
}

.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 24px;
}

.header {
  background: linear-gradient(135deg, #65c18c 0%, #5fb2e2 100%);
  color: #fff;
  padding: 64px 0 48px;
  text-align: center;
}
.title { font-size: 40px; margin: 0 0 8px; }
.subtitle { margin: 0; opacity: .9; }

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  margin-top: -24px;
  padding: 24px;
  box-shadow: 0 6px 24px rgba(0,0,0,.08);
}

.label { display: block; font-weight: 600; margin-bottom: 8px; }
.output-row { display: flex; gap: 8px; align-items: center; }
.output {
  flex: 1;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 16px;
}
.icon-btn {
  border: 1px solid var(--border);
  background: #f0f4f8;
  color: var(--text);
  padding: 8px 12px;
  border-radius: 8px;
  cursor: pointer;
}
.icon-btn:hover { background: #e6edf5; }

.length-row { display: grid; grid-template-columns: auto 120px 1fr; gap: 12px; align-items: center; margin-top: 20px; }
.length-input { padding: 8px; border: 1px solid var(--border); border-radius: 8px; }
.length-slider { width: 100%; }

.options { list-style: none; padding: 0; margin: 16px 0; display: grid; grid-template-columns: 1fr 1fr; gap: 8px 24px; }
.options label { display: flex; align-items: center; gap: 10px; color: var(--muted); }

.actions { display: flex; align-items: center; gap: 12px; margin-top: 16px; }
.primary {
  background: var(--primary);
  color: #fff;
  border: none;
  padding: 10px 16px;
  border-radius: 8px;
  cursor: pointer;
  font-weight: 600;
}
.primary:hover { background: var(--primary-dark); }
.secondary { background: #eef3f8; color: var(--text); border: 1px solid var(--border); padding: 10px 16px; border-radius: 8px; cursor: pointer; }

.toast { margin-left: auto; color: var(--muted); }
.error { color: #c0392b; font-weight: 600; min-height: 20px; }

.footer { text-align: center; color: var(--muted); padding: 24px 0 40px; }

@media (max-width: 640px) {
  .options { grid-template-columns: 1fr; }
  .length-row { grid-template-columns: auto 100px 1fr; }
}