*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --bg: #0f0f0f;
  --surface: #1a1a1a;
  --border: rgba(255, 255, 255, 0.08);
  --text: #ffffff;
  --muted: rgba(255, 255, 255, 0.45);
  --accent: #ff6b35;
}

html, body {
  height: 100%;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
  user-select: none;
  overflow: hidden;
}

.back-link {
  position: fixed;
  top: 1.2rem;
  left: 1.5rem;
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--muted);
  text-decoration: none;
  transition: color 0.2s ease;
  z-index: 10;
}

.back-link:hover {
  color: var(--text);
}

#install-btn {
  position: fixed;
  top: 1.2rem;
  right: 1.5rem;
  background: transparent;
  border: none;
  cursor: pointer;
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--muted);
  padding: 0;
  z-index: 10;
  transition: color 0.2s ease;
  -webkit-tap-highlight-color: transparent;
}

#install-btn:hover {
  color: var(--text);
}

#app {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 4.5rem 1.25rem 2rem;
  min-height: 100%;
}

.tabs {
  display: flex;
  gap: 0.25rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.25rem;
  width: 100%;
  max-width: 420px;
  margin-bottom: 2rem;
}

.tab {
  flex: 1;
  background: transparent;
  border: none;
  border-radius: 7px;
  color: var(--muted);
  cursor: pointer;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  padding: 0.5rem 0.25rem;
  transition: color 0.15s, background 0.15s;
  -webkit-tap-highlight-color: transparent;
}

.tab.active {
  background: var(--accent);
  color: #000;
}

.tab:not(.active):hover {
  color: var(--text);
}

.converter {
  width: 100%;
  max-width: 420px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
}

.row {
  display: flex;
  align-items: center;
  padding: 1.25rem 1.25rem;
  gap: 0.75rem;
}

.row input[type="number"] {
  flex: 1;
  background: transparent;
  border: none;
  color: var(--text);
  font-size: 2rem;
  font-weight: 300;
  min-width: 0;
  outline: none;
  -moz-appearance: textfield;
  user-select: text;
}

.row input[type="number"]::-webkit-outer-spin-button,
.row input[type="number"]::-webkit-inner-spin-button {
  -webkit-appearance: none;
}

.row input[type="number"]:focus {
  color: var(--accent);
}

.row select {
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 500;
  padding: 0.45rem 0.6rem;
  outline: none;
  flex-shrink: 0;
  max-width: 7rem;
  transition: border-color 0.15s;
  -webkit-appearance: none;
  appearance: none;
  text-align: center;
}

.row select:focus {
  border-color: var(--accent);
}

.divider {
  height: 1px;
  background: var(--border);
  margin: 0 1.25rem;
}

#ingredient-wrap {
  padding: 0.85rem 1.25rem 0;
}

#ingredient {
  width: 100%;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  cursor: pointer;
  font-family: inherit;
  font-size: 0.88rem;
  font-weight: 500;
  padding: 0.5rem 0.75rem;
  outline: none;
  margin-bottom: 0.85rem;
  transition: border-color 0.15s;
  -webkit-appearance: none;
  appearance: none;
}

#ingredient:focus {
  border-color: var(--accent);
}

#density-note {
  font-size: 0.62rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  opacity: 0.7;
  text-align: center;
  margin-bottom: 0.85rem;
}