:root {
  color-scheme: dark;
  --bg: #07111f;
  --surface: rgba(13, 29, 48, 0.86);
  --surface-strong: #10243b;
  --surface-soft: #0c1c2f;
  --line: rgba(157, 203, 231, 0.16);
  --line-strong: rgba(133, 215, 231, 0.32);
  --text: #eefaff;
  --muted: #9cb2c4;
  --cyan: #26d9c7;
  --blue: #68b7ff;
  --warning: #f3d08b;
  --shadow: 0 24px 80px rgba(0, 0, 0, 0.28);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; background: var(--bg); }
body { margin: 0; min-width: 320px; min-height: 100vh; background: radial-gradient(circle at 80% -10%, #143655 0, transparent 32rem), var(--bg); color: var(--text); }
button, input, select { font: inherit; }
button, select { cursor: pointer; }
button:focus-visible, input:focus-visible, select:focus-visible { outline: 3px solid rgba(38, 217, 199, 0.36); outline-offset: 2px; }

.ambient { position: fixed; z-index: -1; border-radius: 999px; filter: blur(70px); opacity: .13; pointer-events: none; }
.ambient-one { width: 22rem; height: 22rem; background: #1fd9c8; top: 18rem; left: -12rem; }
.ambient-two { width: 24rem; height: 24rem; background: #408cff; top: 50rem; right: -15rem; }
.shell { width: min(100% - 2rem, 1120px); margin: 0 auto; padding: env(safe-area-inset-top) 0 calc(2rem + env(safe-area-inset-bottom)); }

.topbar { min-height: 5.25rem; display: flex; align-items: center; justify-content: space-between; gap: 1rem; border-bottom: 1px solid var(--line); }
.brand { display: inline-flex; gap: .72rem; align-items: center; color: var(--text); text-decoration: none; }
.brand-mark { display: grid; place-items: center; width: 2.5rem; height: 2.5rem; border: 1px solid var(--line-strong); border-radius: .75rem; background: linear-gradient(145deg, rgba(38,217,199,.14), rgba(104,183,255,.08)); }
.brand-mark svg { width: 1.35rem; fill: none; stroke: var(--cyan); stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
.brand strong { display: block; font-size: .95rem; letter-spacing: -.01em; }
.privacy-chip { flex: none; display: inline-flex; align-items: center; gap: .45rem; color: #bdd0dc; font-size: .78rem; font-weight: 650; }
.privacy-chip span { width: .45rem; height: .45rem; border-radius: 50%; background: var(--cyan); box-shadow: 0 0 0 4px rgba(38,217,199,.1); }

.intro { padding: 3rem 0 2rem; }
.intro h1 { max-width: 700px; margin: 0; font-size: clamp(2.25rem, 8vw, 4.75rem); line-height: .99; letter-spacing: -.055em; }

.calculator-grid { display: grid; gap: 1rem; }
.panel { position: relative; padding: 1.25rem; overflow: hidden; border: 1px solid var(--line); border-radius: 1.25rem; background: linear-gradient(145deg, rgba(16,36,59,.94), rgba(10,24,41,.92)); box-shadow: var(--shadow); }
.primary-panel::before { content: ""; position: absolute; inset: 0 auto auto 0; width: 5rem; height: 2px; background: var(--cyan); }
.target-panel { background: rgba(10, 24, 41, .76); box-shadow: none; }
.panel-heading, .section-heading { display: flex; align-items: flex-start; justify-content: space-between; gap: 1rem; margin-bottom: 1.35rem; }
.panel-heading > div, .section-heading > div:first-child { display: flex; align-items: center; gap: .65rem; }
.step { color: var(--cyan); font: 700 .7rem/1 ui-monospace, SFMono-Regular, Menlo, monospace; letter-spacing: .08em; }
h2 { margin: 0; font-size: 1.08rem; letter-spacing: -.015em; }
.text-button { padding: .35rem .1rem; border: 0; background: transparent; color: var(--muted); font-size: .8rem; font-weight: 700; }
.text-button:hover { color: var(--text); }
.field-grid { display: grid; gap: 1rem; }
.field { display: block; min-width: 0; }
.field > span:first-child, .result-label, .target-result > span { display: block; margin-bottom: .52rem; color: #b4c6d3; font-size: .8rem; font-weight: 700; }
.field > span b { margin-left: .4rem; color: #88a1b4; font-size: .62rem; font-weight: 700; letter-spacing: .04em; text-transform: uppercase; }
.full-field { margin-top: 1rem; }
.input-group, .select-wrap, .output-group { display: flex; width: 100%; min-height: 3.2rem; border: 1px solid var(--line-strong); border-radius: .75rem; background: #081726; transition: border-color .2s, box-shadow .2s; }
.input-group:focus-within, .select-wrap:focus-within { border-color: var(--cyan); box-shadow: 0 0 0 3px rgba(38,217,199,.08); }
input, select { min-width: 0; border: 0; color: var(--text); background: transparent; }
input { width: 100%; padding: 0 .9rem; font-size: 1rem; font-weight: 700; }
select {
  appearance: none;
  padding: 0 1.8rem 0 .65rem;
  color: #c8dae5;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 12 8'%3E%3Cpath d='m2 2 4 4 4-4' fill='none' stroke='%239cb2c4' stroke-width='1.7' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right .65rem center;
  background-size: .68rem auto;
  font-size: .82rem;
  font-weight: 700;
}
select option { color: #07111f; background: #ffffff; }
select option:checked { color: #ffffff; background: #2b8fbd linear-gradient(0deg, #2b8fbd, #2b8fbd); }
.input-group select { flex: 0 0 8rem; width: 8rem; border-left: 1px solid var(--line); }
.select-wrap select { width: 100%; padding-left: .9rem; }
.field-help { display: block; padding-top: .42rem; color: var(--muted); font-size: .73rem; line-height: 1.4; }
.field-error { display: block; min-height: 1rem; padding-top: .25rem; color: #ffb8ad; font-size: .73rem; }
.result-card { display: flex; align-items: end; justify-content: space-between; gap: 1rem; margin-top: 1.15rem; padding: 1.2rem; border: 1px solid rgba(38,217,199,.27); border-radius: 1rem; background: linear-gradient(110deg, rgba(38,217,199,.11), rgba(104,183,255,.07)); }
.result-card strong { display: block; color: #eaffff; font: 600 clamp(2.65rem, 12vw, 4.2rem)/.95 ui-monospace, SFMono-Regular, Menlo, monospace; letter-spacing: -.07em; }
.result-card select { min-width: 6.4rem; height: 2.4rem; padding-left: .6rem; border: 1px solid var(--line); border-radius: .6rem; background: rgba(4,16,28,.45); }
.target-fields { display: grid; gap: 1rem; }
.dose-result { margin-top: 1rem; padding: 1.15rem; border: 1px solid rgba(38,217,199,.24); border-radius: 1rem; background: linear-gradient(110deg, rgba(38,217,199,.10), rgba(104,183,255,.06)); }
.dose-result > span { display: block; margin-bottom: .45rem; color: #b4c6d3; font-size: .8rem; font-weight: 700; }
.dose-result > div { display: flex; align-items: baseline; gap: .6rem; }
.dose-result strong { font: 600 2.8rem/1 ui-monospace, SFMono-Regular, Menlo, monospace; letter-spacing: -.06em; }
.dose-result b { color: var(--cyan); font-size: .9rem; }
.dose-result p { margin: .65rem 0 0; color: #c8d9e4; font-size: .8rem; line-height: 1.5; }
.dose-result.invalid { border-color: rgba(255,184,173,.42); background: rgba(113,43,43,.14); }
.syringe-visual { position: relative; height: 5.5rem; margin-top: 1rem; padding: 0 .5rem; overflow: hidden; border: 1px solid var(--line-strong); border-radius: .8rem; background: #f8fbfd; }
.syringe-scale { position: absolute; inset: 1.2rem .6rem auto; height: 2rem; background-image: repeating-linear-gradient(to right, #172533 0 2px, transparent 2px calc(10%)); background-size: 10% 55%; background-repeat: repeat-x; background-position: left top; }
.syringe-scale::after { content: ""; position: absolute; inset: 0; border-top: 2px solid #172533; }
.syringe-labels { position: absolute; inset: 3.1rem .6rem auto; display: flex; justify-content: space-between; color: #172533; font: 700 .66rem/1 ui-monospace, SFMono-Regular, Menlo, monospace; }
.syringe-fill { position: absolute; top: 1.2rem; bottom: 1.6rem; left: .6rem; width: 20%; max-width: calc(100% - 1.2rem); border-radius: .18rem 0 0 .18rem; background: rgba(29,166,214,.22); border-right: 3px solid #0da9df; transition: width .2s ease; }
.syringe-marker { position: absolute; top: .18rem; left: 20%; transform: translateX(-50%); color: #066c91; font: 800 .7rem/1 ui-monospace, SFMono-Regular, Menlo, monospace; transition: left .2s ease; }
.syringe-marker::after { content: ""; display: block; width: 2px; height: .8rem; margin: .18rem auto 0; background: #0da9df; }
.conversion-note { margin: .85rem 0 0; color: var(--muted); font-size: .72rem; line-height: 1.5; }

@media (min-width: 640px) {
  .shell { width: min(100% - 3rem, 1120px); }
  .panel { padding: 1.6rem; }
  .field-grid { grid-template-columns: 1fr 1fr; }
  .target-fields { grid-template-columns: 1fr 1fr; }
}

@media (min-width: 900px) {
  .intro { padding: 3.75rem 0 2.5rem; }
  .calculator-grid { grid-template-columns: minmax(0, 1.25fr) minmax(300px, .75fr); }
  .panel { padding: 1.8rem; }
  .target-panel { display: flex; flex-direction: column; }
}

@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } * { transition: none !important; } }