Below are two files. Copy them as-is:

---

**/assets/main.css**

```css
/* ========== Global Reset & Theme Vars ========== */
* { box-sizing: border-box; }
:root {
  --bg:#0f172a; --card:#111827; --fg:#e5e7eb; --muted:#9ca3af; --acc:#22d3ee; --line:#1f2937;
}
html, body {
  background: var(--bg);
  color: var(--fg);
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Ubuntu, "Helvetica Neue", Arial, sans-serif;
  margin: 0; padding: 0;
}

/* ========== Layout ========== */
.wrap { max-width: 1100px; margin: 32px auto; padding: 0 16px; }

h1 { font-size: 22px; margin: 0 0 16px; color: #fff; text-align: center; }

.grid { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
@media (max-width: 980px){ .grid { grid-template-columns: 1fr; } }

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 16px;
  box-shadow: 0 10px 20px rgba(0,0,0,.25);
  overflow: hidden;
  position: relative;
}

/* ========== Typography & Controls ========== */
label { display: flex; align-items: center; gap: 8px; font-size: 13px; color: var(--muted); margin-bottom: 6px; }

input, select, button { font-size: 14px; }

input, select {
  width: 100%;
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid #374151;
  background: #0b1220;
  color: #e5e7eb;
  outline: none;
}

input:focus, select:focus { border-color: var(--acc); }

input[readonly] { opacity: .95; cursor: text; background: #0b1220; }

.row { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
@media (max-width: 640px){ .row { grid-template-columns: 1fr; } }

.btns { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 14px; }

.btns button {
  flex: 1 1 200px; min-width: 180px; max-width: 100%;
  padding: 10px 14px; border: 1px solid #374151; border-radius: 10px;
  background: #0b1220; color: #fff; cursor: pointer; white-space: nowrap;
}

.btns button.primary { background: linear-gradient(90deg,#06b6d4,#3b82f6); border: none; }

textarea {
  width: 100%; min-height: 320px; padding: 12px;
  border-radius: 12px; border: 1px solid #374151;
  background: #0b1220; color: #e5e7eb;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, "Roboto Mono", monospace;
}

.errors { background: #3f1d1d; border: 1px solid #7f1d1d; color: #fecaca; padding: 10px 12px; border-radius: 10px; margin-bottom: 12px; }

.ok { background: #12321f; border: 1px solid #14532d; color: #dcfce7; padding: 10px 12px; border-radius: 10px; margin-top: 12px; white-space: pre-wrap; }

/* ========== Segmented Controls ========== */
.seg { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 6px; }
.seg button { padding: 8px 10px; border-radius: 999px; border: 1px solid #374151; background: #0b1220; color: #e5e7eb; cursor: pointer; }
.seg button.active { border-color: #3b82f6; outline: 2px solid rgba(59,130,246,.35); }

.inline { display: flex; gap: 10px; align-items: center; justify-content: space-between; }
.pill { display: inline-block; padding: 6px 10px; border-radius: 999px; background: #0b1220; border: 1px solid #334155; font-size: 12px; color: #cbd5e1; cursor: pointer; }

/* ========== Tooltip / Popover ========== */
.tipbtn { margin-left: auto; background: #0b1220; border: 1px solid #334155; color: #cbd5e1; border-radius: 999px; padding: 6px 9px; cursor: pointer; position: relative; }
.popover { position: fixed; z-index: 9999; max-width: 320px; background: #0b1220; color: #cbd5e1; border: 1px solid #334155; border-radius: 10px; padding: 10px 12px; box-shadow: 0 10px 30px rgba(0,0,0,.45); display: none; }

/* ========== Symbol Suggest Dropdown ========== */
.suggest { position: absolute; z-index: 99; background: #0b1220; border: 1px solid #334155; border-radius: 10px; width: 100%; max-height: 220px; overflow: auto; display: none; }
.suggest div { padding: 8px 10px; cursor: pointer; }
.suggest div:hover { background: #111827; }
.relative { position: relative; }

/* ========== Sell Cards ========== */
.cards { display: grid; grid-template-columns: 1fr; gap: 10px; }
.card-opt { border: 1px solid #334155; border-radius: 12px; padding: 12px; background: #0b1220; }
.card-opt.active { outline: 2px solid rgba(59,130,246,.35); border-color: #3b82f6; }
.card-opt h4 { margin: 0 0 6px; font-size: 14px; color: #e5e7eb; }
.hint { font-size: 12px; color: #9ca3af; margin-top: 4px; }
.desc { font-size: 12px; color: #cbd5e1; }
.muted { color: #9ca3af; font-size: 12px; margin-top: 6px; }