/* =====================================================================
   LEAF FUSION PLASMA THEME — html[data-theme="leaf"]
   Plasma is ionised gas: the palette is the glow discharge itself, a
   violet-indigo ground under electric cyan, with the academy's gold
   kept for certification so the shell still reads as Seoulogy.
   ===================================================================== */
html[data-theme="leaf"] {
  --forest: #171a2e;
  --forest-2: #1f2440;
  --moss: #3d4575;
  --sea: #6f7fd4;
  --spume: #a6b4f5;
  --glow: #d8e4ff;

  --gold: #c9a961;
  --gold-lo: #8f7539;
  --gold-hi: #f0dda7;

  --surface: #10121f;
  --surface-2: #161a2c;
  --surface-3: #1e2440;
  --line: rgba(166, 180, 245, 0.13);
  --line-2: rgba(166, 180, 245, 0.26);
  --text: #e7ebff;
  --text-dim: #b0b8da;
  --text-faint: #828aad;
}
html[data-theme="leaf"] body::before {
  background:
    /* the arc, top left */
    radial-gradient(1100px 650px at 10% -12%, rgba(110, 170, 255, 0.18), transparent 60%),
    /* the violet discharge field */
    radial-gradient(900px 620px at 90% 4%, rgba(104, 76, 190, 0.32), transparent 62%),
    /* a cyan bloom where the tip meets skin */
    radial-gradient(620px 420px at 74% 62%, rgba(96, 206, 230, 0.12), transparent 64%),
    radial-gradient(1000px 800px at 50% 110%, rgba(8, 9, 18, 0.92), transparent 60%),
    linear-gradient(180deg, #141729 0%, #10121f 52%, #0a0b14 100%);
}

/* a faint electrical shimmer along a lesson's section rules, slow enough
   to read as atmosphere rather than decoration */
html[data-theme="leaf"] .sec-head { position: relative; }
html[data-theme="leaf"] .sec-head::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -1px; height: 1px;
  background: linear-gradient(90deg, transparent, rgba(166, 180, 245, 0.5), transparent);
  background-size: 220% 100%;
  animation: leafSheen 7s linear infinite;
}
@keyframes leafSheen { from { background-position: 180% 0; } to { background-position: -80% 0; } }
@media (prefers-reduced-motion: reduce) { html[data-theme="leaf"] .sec-head::after { animation: none; } }