:root {
  --bg: #f6f7f9;
  --card: #ffffff;
  --ink: #1a1f29;
  --muted: #6b7280;
  --line: #e4e7ec;
  --accent: #1f6feb;
  --accent-ink: #ffffff;
  --ok: #0a7d4b;
  --warn: #b45309;
  --danger: #b42318;
  --radius: 12px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  font-size: 16px;
  line-height: 1.5;
  -webkit-text-size-adjust: 100%;
}

.wrap {
  max-width: 720px;
  margin: 0 auto;
  padding: 20px 16px 48px;
}

.head { margin: 8px 0 16px; }
.head h1 {
  font-size: 26px;
  line-height: 1.2;
  margin: 0 0 6px;
  letter-spacing: -0.01em;
}
.tagline {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
  box-shadow: 0 1px 2px rgba(16,24,40,.04);
}

/* ---- purchase rows ---- */
.row-head,
.row {
  display: grid;
  grid-template-columns: 1fr 1fr 40px;
  gap: 8px;
  align-items: center;
}
.row-head {
  margin-bottom: 6px;
}
.row-head span {
  font-size: 13px;
  font-weight: 600;
  color: var(--ink);
}
.rows { display: flex; flex-direction: column; gap: 8px; }
.row input { text-align: left; }

.del {
  width: 40px;
  height: 44px;
  font-size: 20px;
  line-height: 1;
  color: var(--muted);
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 8px;
  cursor: pointer;
}
.del:hover:enabled { color: var(--danger); border-color: #f0c2bd; }
.del:disabled { opacity: .35; cursor: default; }

.row-actions { margin-top: 10px; }
.add-btn {
  height: 40px;
  padding: 0 14px;
  font-size: 14px;
  font-weight: 600;
  color: var(--accent);
  background: #fff;
  border: 1px dashed var(--accent);
  border-radius: 8px;
  cursor: pointer;
}
.add-btn:active { transform: translateY(1px); }

.f { display: flex; flex-direction: column; gap: 6px; margin-top: 14px; }
.f > span { font-size: 13px; font-weight: 600; color: var(--ink); }
.f > span i { font-style: normal; font-weight: 400; color: var(--muted); }

input {
  width: 100%;
  height: 44px;
  padding: 0 12px;
  font-size: 16px; /* >=16px stops iOS zoom-on-focus */
  color: var(--ink);
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 8px;
  appearance: none;
  -webkit-appearance: none;
}
input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(31,111,235,.15);
}

.hint { font-size: 12px; color: var(--muted); font-style: normal; font-weight: 400; }

.calc-btn {
  width: 100%;
  height: 48px;
  margin-top: 16px;
  font-size: 16px;
  font-weight: 600;
  color: var(--accent-ink);
  background: var(--accent);
  border: none;
  border-radius: 8px;
  cursor: pointer;
}
.calc-btn:active { transform: translateY(1px); }

.result { margin-top: 18px; border-top: 1px solid var(--line); padding-top: 16px; }
.res-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}
.res-grid + .res-grid { margin-top: 12px; }
.res {
  background: #f3f6fb;
  border: 1px solid #e3ebf7;
  border-radius: 10px;
  padding: 12px 14px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  min-width: 0;
}
.res-wide { grid-column: 1 / -1; }
.res > span { font-size: 12px; color: var(--muted); }
.res > b {
  font-size: 20px;
  font-weight: 700;
  color: var(--ink);
  word-break: break-word;
}
.res > b.up { color: var(--ok); }
.res > b.down { color: var(--danger); }

.res-note { font-size: 13px; color: var(--muted); margin: 12px 0 0; }
.res-note.warn { color: var(--warn); }

.worked {
  margin: 12px 0 0;
  padding: 10px 12px;
  font-size: 13px;
  color: #384049;
  background: #fbfcfe;
  border: 1px dashed var(--line);
  border-radius: 8px;
  word-break: break-word;
}

.copy-btn {
  margin-top: 14px;
  height: 42px;
  padding: 0 18px;
  font-size: 14px;
  font-weight: 600;
  color: var(--accent);
  background: #fff;
  border: 1px solid var(--accent);
  border-radius: 8px;
  cursor: pointer;
}
.copy-btn.done { color: var(--ok); border-color: var(--ok); }

.doc { margin-top: 28px; }
.doc h2 {
  font-size: 19px;
  margin: 26px 0 10px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
}
.doc h2:first-child { border-top: none; padding-top: 0; }
.doc h3 { font-size: 15px; margin: 18px 0 6px; }
.doc p, .doc li { font-size: 14px; color: #384049; }
.doc ul { padding-left: 20px; margin: 8px 0; }
.doc li { margin: 4px 0; }
.formula {
  padding: 10px 12px;
  background: #fbfcfe;
  border: 1px solid var(--line);
  border-radius: 8px;
  font-size: 13px;
  overflow-x: auto;
}

.foot {
  margin-top: 32px;
  font-size: 12px;
  color: var(--muted);
  text-align: center;
}

/* ---- site footer nav ---- */
.sitenav {
  margin-top: 14px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px 18px;
}
.sitenav a {
  font-size: 14px;
  color: var(--accent);
  text-decoration: none;
  padding: 6px 2px;
}
.sitenav a:hover,
.sitenav a:focus { text-decoration: underline; }

/* ---- simple content pages (about / privacy / contact) ---- */
.page-title {
  font-size: 24px;
  line-height: 1.2;
  margin: 8px 0 4px;
  letter-spacing: -0.01em;
}
.page-lede {
  margin: 0 0 4px;
  color: var(--muted);
  font-size: 14px;
}
.doc .page-title { border-top: none; padding-top: 0; margin-top: 8px; }
.doc a { color: var(--accent); }
.mailbox {
  display: inline-block;
  margin: 4px 0 10px;
  padding: 10px 14px;
  background: #f3f6fb;
  border: 1px solid #e3ebf7;
  border-radius: 10px;
  font-size: 16px;
  font-weight: 700;
  color: var(--ink);
  word-break: break-all;
}

/* ---- phone width ---- */
@media (max-width: 480px) {
  .wrap { padding: 16px 12px 40px; }
  .head h1 { font-size: 22px; }
  .card { padding: 14px; }
  .row-head, .row { grid-template-columns: 1fr 1fr 38px; gap: 6px; }
  .del { width: 38px; }
  .res-grid { grid-template-columns: 1fr; }
  .res > b { font-size: 19px; }
}