:root {
  --bg: #fffaf3;
  --bg-elev: #ffffff;
  --card: #ffffff;
  --text: #43321d;
  --text-soft: #8a6f4f;
  --border: #f0e2cf;
  --primary: #d97706;
  --primary-soft: #fcecd4;
  --primary-strong: #b45309;
  --accent: #ec4899;
  --accent-soft: #fce0ef;
  --result-bg: linear-gradient(135deg, #fef3e2, #fde7c9);
  --shadow: 0 6px 24px rgba(180, 83, 9, 0.12);
  --focus: #b45309;
  --radius: 16px;
  --radius-sm: 10px;
}

[data-theme="dark"] {
  --bg: #1c160f;
  --bg-elev: #271e14;
  --card: #2a2014;
  --text: #f4e7d4;
  --text-soft: #c2a984;
  --border: #3d2f1d;
  --primary: #f59e0b;
  --primary-soft: #4a3415;
  --primary-strong: #fbbf24;
  --accent: #f472b6;
  --accent-soft: #4a2236;
  --result-bg: linear-gradient(135deg, #3a2a16, #45331b);
  --shadow: 0 6px 24px rgba(0, 0, 0, 0.4);
  --focus: #fbbf24;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  max-width: 100%;
  overflow-x: hidden;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  padding-bottom: env(safe-area-inset-bottom);
  -webkit-text-size-adjust: 100%;
}

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--primary);
  color: #fff;
  padding: 10px 16px;
  border-radius: 0 0 var(--radius-sm) 0;
  z-index: 100;
}
.skip-link:focus { left: 0; }

/* HEADER */
.app-header {
  background: var(--bg-elev);
  border-bottom: 1px solid var(--border);
  padding-top: env(safe-area-inset-top);
  position: sticky;
  top: 0;
  z-index: 20;
}
.header-inner {
  max-width: 640px;
  margin: 0 auto;
  padding: 12px 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}
.brand { display: flex; align-items: center; gap: 12px; min-width: 0; }
.brand-icon { display: flex; flex: 0 0 auto; }
.brand-text { min-width: 0; }
.brand-text h1 {
  margin: 0;
  font-size: 1.25rem;
  letter-spacing: -0.01em;
  color: var(--primary-strong);
}
.tagline {
  margin: 0;
  font-size: 0.78rem;
  color: var(--text-soft);
}

.icon-btn {
  flex: 0 0 auto;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: var(--card);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background .2s, transform .15s;
}
.icon-btn:hover { background: var(--primary-soft); }
.icon-btn:active { transform: scale(0.93); }
.theme-icon { width: 22px; height: 22px; display: block; }
.theme-icon::before {
  content: "🌙";
  font-size: 20px;
  line-height: 22px;
}
[data-theme="dark"] .theme-icon::before { content: "☀️"; }

/* TABS */
.tabs {
  max-width: 640px;
  margin: 0 auto;
  padding: 12px 16px 4px;
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}
.tab {
  flex: 1 1 auto;
  min-width: 120px;
  padding: 10px 12px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--text-soft);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all .18s;
}
.tab:hover { border-color: var(--primary); color: var(--text); }
.tab.is-active {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
  box-shadow: var(--shadow);
}

/* MAIN / PANELS */
main {
  max-width: 640px;
  margin: 0 auto;
  padding: 8px 16px 24px;
}
.panel { display: none; }
.panel.is-active { display: block; animation: fade .25s ease; }

@keyframes fade {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

/* CARD */
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
  box-shadow: var(--shadow);
}
.card h2 {
  margin: 0 0 6px;
  font-size: 1.15rem;
  color: var(--text);
}
.hint {
  margin: 0 0 16px;
  font-size: 0.85rem;
  color: var(--text-soft);
}

/* FIELDS */
.field { display: block; margin-bottom: 14px; }
.field-label {
  display: block;
  font-size: 0.82rem;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text-soft);
}
.control {
  width: 100%;
  padding: 13px 14px;
  font-size: 1rem;
  border-radius: var(--radius-sm);
  border: 1.5px solid var(--border);
  background: var(--bg);
  color: var(--text);
  appearance: none;
  -webkit-appearance: none;
  transition: border-color .15s, box-shadow .15s;
}
select.control {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%23b45309' stroke-width='2' fill='none' stroke-linecap='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 14px center;
  padding-right: 36px;
}
.control:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-soft);
}

/* SEGMENTED */
.seg {
  display: flex;
  gap: 6px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 4px;
  margin-bottom: 14px;
  flex-wrap: wrap;
}
.seg-btn {
  flex: 1 1 120px;
  padding: 9px 8px;
  border: none;
  border-radius: 8px;
  background: transparent;
  color: var(--text-soft);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  transition: all .15s;
}
.seg-btn.is-active {
  background: var(--primary);
  color: #fff;
}

/* QUICK CHIPS */
.quick {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 16px;
}
.chip {
  padding: 8px 14px;
  border-radius: 999px;
  border: 1.5px solid var(--accent-soft);
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 0.85rem;
  font-weight: 700;
  cursor: pointer;
  transition: all .15s;
}
.chip:hover { border-color: var(--accent); }
.chip:active { transform: scale(0.94); }

/* RESULT */
.result {
  background: var(--result-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 18px;
  text-align: center;
  margin-top: 4px;
}
.result-value {
  font-size: 1.7rem;
  font-weight: 800;
  color: var(--primary-strong);
  letter-spacing: -0.01em;
  word-break: break-word;
}
.result-value small {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-soft);
  margin-top: 6px;
}

.density-note {
  margin: 12px 0 0;
  font-size: 0.78rem;
  color: var(--text-soft);
  text-align: center;
}

/* INFO BOX (Umluft) */
.info-box {
  margin-top: 14px;
  padding: 14px 16px;
  border-radius: var(--radius-sm);
  background: var(--accent-soft);
  border: 1px solid var(--accent-soft);
  color: var(--text);
  font-size: 0.88rem;
}
.info-box:empty { display: none; }
.info-box strong { color: var(--accent); }

/* GAS */
.gas-block {
  margin-top: 16px;
  border-top: 1px solid var(--border);
  padding-top: 12px;
}
.gas-block summary {
  cursor: pointer;
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--primary-strong);
}
.gas-list {
  list-style: none;
  margin: 12px 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: 1fr;
  gap: 6px;
}
.gas-list li {
  display: flex;
  justify-content: space-between;
  font-size: 0.85rem;
  padding: 7px 12px;
  background: var(--bg);
  border-radius: 8px;
  border: 1px solid var(--border);
}
.gas-list li span:last-child { font-weight: 700; color: var(--primary-strong); }

/* VOLUME GRID */
.vol-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}
@media (max-width: 420px) {
  .vol-grid { grid-template-columns: 1fr; }
}

/* FOOTER */
.app-footer {
  max-width: 640px;
  margin: 0 auto;
  padding: 8px 16px 28px;
  text-align: center;
}
.app-footer p {
  margin: 0;
  font-size: 0.75rem;
  color: var(--text-soft);
}

/* TOAST */
.toast {
  position: fixed;
  left: 50%;
  bottom: calc(20px + env(safe-area-inset-bottom));
  transform: translateX(-50%) translateY(20px);
  background: var(--text);
  color: var(--bg);
  padding: 12px 20px;
  border-radius: 999px;
  font-size: 0.88rem;
  font-weight: 600;
  box-shadow: 0 8px 24px rgba(0,0,0,.25);
  opacity: 0;
  transition: opacity .25s, transform .25s;
  z-index: 200;
  max-width: 88vw;
  text-align: center;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

/* FOCUS VISIBILITY */
button:focus-visible,
.control:focus-visible,
summary:focus-visible,
a:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 2px;
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
  }
}