:root {
  --bg: #eef0f3; --card: #ffffff; --text: #15171c; --muted: #6b7280; --line: #e5e7eb;
  --accent: #121318; --accent-text: #ffffff; --solved: #e6f2ea; --solved-line: #2e7d4f;
  --err: #b42318;
}
* { box-sizing: border-box; }
body {
  margin: 0; background: var(--bg); color: var(--text);
  font: 15px/1.5 "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
main { max-width: 760px; margin: 24px auto 48px; padding: 24px; background: var(--card); border-radius: 18px; }
@media (max-width: 560px) { main { margin: 0; border-radius: 0; padding: 20px 16px; } }
main h1 { font-size: 1.6rem; margin: 8px 0 4px; }
main h2 { font-size: 1.1rem; margin: 28px 0 8px; color: var(--muted); }
a { color: #4f46e5; }
.back { font-size: 0.9rem; }
.eq {
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif; font-size: 1.15rem;
  padding: 12px 14px; border: 1px solid var(--line); border-radius: 8px; overflow-x: auto;
}
.how { color: var(--muted); font-size: 0.95rem; }
.row {
  display: grid; grid-template-columns: 1fr 140px; grid-template-areas: "name name" "input unit";
  gap: 4px 10px; align-items: center; padding: 10px 0; border-bottom: 1px solid var(--line);
}
.row .name { grid-area: name; }
.row input { grid-area: input; }
.row .unit { grid-area: unit; color: var(--muted); font-size: 0.9rem; }
input {
  width: 100%; font: inherit; padding: 8px 10px; color: var(--text); background: var(--bg);
  border: 1px solid var(--line); border-radius: 6px;
}
input:focus { outline: 2px solid var(--accent); outline-offset: 1px; }
input.solved { background: var(--solved); border-color: var(--solved-line); font-weight: 600; }
.buttons { display: flex; gap: 10px; margin-top: 18px; }
button {
  font: inherit; font-weight: 600; padding: 10px 22px; border-radius: 6px; cursor: pointer;
  border: 1px solid var(--accent); background: var(--accent); color: var(--accent-text);
}
button.secondary { background: transparent; color: var(--accent); }
#msg { min-height: 1.5em; margin-top: 14px; font-weight: 600; }
#msg.err { color: var(--err); }
.src, .disclaimer { color: var(--muted); font-size: 0.85rem; }
.disclaimer { margin-top: 32px; border-top: 1px solid var(--line); padding-top: 12px; }
ul.list { list-style: none; padding: 0; margin: 0; }
ul.list li { padding: 8px 0; border-bottom: 1px solid var(--line); }
@media (min-width: 560px) {
  .row { grid-template-columns: 1fr 160px 150px; grid-template-areas: "name input unit"; }
}

/* OEMS banner (copied from the APF calculator) */
/* Header */
.topbar {
  position: relative;
  color: #fff;
  background:
    linear-gradient(rgba(255, 255, 255, 0.035) 1px, transparent 1px) 0 0 / 32px 32px,
    linear-gradient(90deg, rgba(255, 255, 255, 0.035) 1px, transparent 1px) 0 0 / 32px 32px,
    linear-gradient(100deg, #0a1631 0%, #0f2b55 50%, #1b4f86 100%);
  box-shadow: 0 6px 14px rgba(15, 23, 42, 0.18);
}

/* Fade the grid in toward the right, as in the design */
.topbar::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(100deg, #0a1631 0%, rgba(15, 43, 85, 0.85) 45%, rgba(27, 79, 134, 0) 80%);
  pointer-events: none;
}

.topbar::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 4px;
  background: linear-gradient(90deg, #38bdf8 0%, #6366f1 50%, #38bdf8 100%);
}

.topbar-inner {
  position: relative;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 24px;
  padding-top: 22px;
  padding-bottom: 22px;
}

.brand { display: flex; flex-direction: column; gap: 4px; }

.brand-name {
  font-size: 2rem;
  font-weight: 800;
  line-height: 1;
  letter-spacing: -0.04em;
}

.brand-full {
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: #cbd5e1;
}

.tag {
  padding-left: 18px;
  border-left: 1px solid rgba(255, 255, 255, 0.25);
  font-size: 0.9rem;
  color: #dbe4f0;
  text-align: right;
}

.wrap {
  max-width: 1136px;
  margin: 0 auto;
  padding-left: 16px;
  padding-right: 16px;
}

@media (max-width: 520px) {
  .tag { display: none; }
  .brand-name { font-size: 1.7rem; }
  .brand-full { font-size: 0.6rem; letter-spacing: 0.14em; }
}
.copyright { color: var(--muted); font-size: 0.75rem; }