:root {
  --ink: #102247;
  --muted: #53627d;
  --line: #cbd8eb;
  --bg: #eef5ff;
  --panel: #ffffff;
  --accent: #087edb;
  --accent-dark: #0755a1;
  --cyan: #09c6ee;
  --coral: #e85d5d;
  --yellow: #f4c95d;
  --accent-ink: #ffffff;
  --error: #a9363d;
  --error-bg: #fff0ef;
  --ok: #176d54;
  --shadow: 0 14px 34px rgba(16, 34, 71, 0.1);
}

* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: 'Trebuchet MS', 'Segoe UI', sans-serif;
  background: linear-gradient(135deg, #eef5ff 0%, #f8fbff 52%, #e6fbff 100%);
  color: var(--ink);
  min-height: 100vh;
}
body::before {
  content: '';
  position: fixed;
  inset: 0;
  pointer-events: none;
  opacity: 0.28;
  background-image: radial-gradient(#8ec9e8 0.7px, transparent 0.7px);
  background-size: 18px 18px;
}
a { color: var(--accent-dark); text-decoration: none; font-weight: 700; }
a:hover { color: var(--coral); text-decoration: underline; }

header.topbar {
  position: relative;
  z-index: 1;
  background: #071a3b;
  border-bottom: 4px solid var(--cyan);
  padding: 0.7rem clamp(1rem, 4vw, 3rem);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  box-shadow: 0 8px 20px rgba(7, 26, 59, 0.18);
}
header.topbar .brand {
  display: inline-flex;
  align-items: center;
  gap: 0.65rem;
  color: #fff;
  font-size: 1.25rem;
  font-weight: 900;
  letter-spacing: 0.13em;
}
header.topbar .brand-mark {
  display: grid;
  place-items: center;
  width: 2.25rem;
  height: 2.25rem;
  border: 4px solid var(--cyan);
  border-radius: 50%;
  color: #fff;
  font-size: 1.25rem;
  line-height: 1;
  box-shadow: 0 0 0 4px rgba(9, 198, 238, 0.16);
}
header.topbar .brand-name { color: #fff; }
header.topbar .brand-name strong { color: var(--cyan); }
header.topbar .brand-tagline { display: block; color: #a9c9ee; font-size: 0.55rem; letter-spacing: 0.2em; font-weight: 600; }
header.topbar nav { display: flex; align-items: center; flex-wrap: wrap; gap: 0.35rem; }
header.topbar nav a { margin: 0; padding: 0.45rem 0.7rem; color: #d9ebff; border-radius: 6px; }
header.topbar nav a:hover { color: #fff; background: rgba(9, 198, 238, 0.18); text-decoration: none; }
header.topbar nav span { color: #a9c9ee !important; margin: 0 0.45rem !important; font-size: 0.82rem; }

main { position: relative; z-index: 1; max-width: 1080px; margin: 2.5rem auto; padding: 0 1.5rem; }
h1 { color: var(--ink); font-size: clamp(1.55rem, 3vw, 2.15rem); margin: 0 0 0.65rem; letter-spacing: -0.02em; }
h2 { color: var(--accent-dark); font-size: 1.1rem; margin-top: 0; }
p { line-height: 1.55; }
code { color: var(--accent-dark); background: #e6f5ff; border-radius: 4px; padding: 0.08rem 0.28rem; }

.panel {
  background: rgba(255, 255, 255, 0.94);
  border: 1px solid var(--line);
  border-top: 4px solid var(--cyan);
  border-radius: 10px;
  padding: clamp(1rem, 3vw, 1.6rem);
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow);
}

table { width: 100%; border-collapse: collapse; }
th, td { text-align: left; padding: 0.7rem 0.6rem; border-bottom: 1px solid #dce6f3; font-size: 0.92rem; }
th { color: var(--accent-dark); font-weight: 800; background: #f1f8ff; }
tr:hover td { background: #f8fcff; }

.btn {
  display: inline-block;
  background: linear-gradient(135deg, var(--accent), var(--accent-dark));
  color: var(--accent-ink);
  border: none;
  border-radius: 6px;
  padding: 0.58rem 1rem;
  font-size: 0.9rem;
  font-weight: 800;
  cursor: pointer;
  box-shadow: 0 5px 12px rgba(8, 126, 219, 0.2);
}
.btn:hover { color: #fff; opacity: 0.92; text-decoration: none; transform: translateY(-1px); }
.btn.secondary { background: #e7f5ff; color: var(--accent-dark); box-shadow: none; }
.btn.danger { background: var(--coral); box-shadow: 0 5px 12px rgba(232, 93, 93, 0.2); }

form.inline { display: inline; }
label { display: block; font-size: 0.85rem; color: var(--accent-dark); font-weight: 800; margin: 0.85rem 0 0.3rem; }
input[type=text], input[type=password], input[type=number], input[type=file], textarea, select {
  width: 100%;
  padding: 0.62rem 0.7rem;
  border: 1px solid #b9cce4;
  border-radius: 6px;
  font-size: 0.95rem;
  font-family: inherit;
  color: var(--ink);
  background: #fbfdff;
}
input:focus, textarea:focus, select:focus, math-field:focus { outline: 3px solid rgba(9, 198, 238, 0.25); border-color: var(--accent); }
textarea { min-height: 4.5rem; resize: vertical; }
.row { display: flex; gap: 1rem; flex-wrap: wrap; }
.row > div { flex: 1; min-width: 160px; }

.error-box { background: var(--error-bg); color: var(--error); border: 1px solid #f0b9b6; border-left: 5px solid var(--coral); border-radius: 6px; padding: 0.75rem 1rem; margin-bottom: 1rem; font-size: 0.9rem; }
.error-box ul { margin: 0.3rem 0 0; padding-left: 1.2rem; }

.type-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 1rem; }
.type-card { position: relative; overflow: hidden; background: var(--panel); border: 1px solid var(--line); border-radius: 10px; padding: 1.2rem; box-shadow: var(--shadow); }
.type-card::after { content: ''; position: absolute; width: 70px; height: 70px; right: -24px; top: -26px; border-radius: 50%; background: var(--yellow); opacity: 0.75; }
.type-card:nth-child(3n + 2)::after { background: var(--cyan); }
.type-card:nth-child(3n)::after { background: #ff9d76; }
.type-card .count { position: relative; z-index: 1; color: var(--accent-dark); font-size: 2rem; font-weight: 900; }
.type-card .label { color: var(--muted); font-size: 0.85rem; }
.type-card .links { margin-top: 0.8rem; font-size: 0.85rem; }
.type-card .links a { margin-right: 0.75rem; }

.formula-bar { border: 2px dashed #8ed8ed; border-radius: 10px; padding: 0.9rem; margin: 0.75rem 0 1.25rem; background: #edfcff; }
.formula-bar .hint { color: var(--muted); font-size: 0.8rem; margin-top: 0.55rem; }
math-field { display: block; width: 100%; font-size: 1.1rem; border: 1px solid #9ed2e5; border-radius: 6px; padding: 0.4rem; background: #fff; }
.preview-pane { border: 1px solid #b9d7e7; border-radius: 6px; padding: 0.75rem; background: #f2fbff; min-height: 2rem; font-size: 1rem; }
.preview-label { font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.04em; color: var(--accent-dark); font-weight: 800; margin: 0.6rem 0 0.35rem; }
.options-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0 1rem; }
footer.hint-footer { text-align: center; color: var(--muted); font-size: 0.8rem; margin: 2rem 0; }

@media (max-width: 680px) {
  header.topbar { align-items: flex-start; flex-direction: column; }
  header.topbar nav { width: 100%; }
  header.topbar nav span { order: 3; width: 100%; margin: 0.25rem 0 !important; }
  main { margin-top: 1.5rem; padding: 0 1rem; }
  .options-grid { grid-template-columns: 1fr; }
  .panel { padding: 1rem; overflow-x: auto; }
  table { min-width: 620px; }
}