:root {
  --bg: #f7f7f9;
  --panel: #ffffff;
  --text: #1c1e21;
  --muted: #6b7280;
  --border: #e2e4e9;
  --accent: #007a3d;
  --accent-hover: #005f30;
  --ok: #16803c;
  --ok-bg: #eafaf0;
  --bad: #c0362c;
  --bad-bg: #fdecea;
  --code-bg: #f0f1f5;
  --link: #007a3d;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Pretendard", "Noto Sans KR", sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #16181d;
    --panel: #1e2127;
    --text: #e7e9ee;
    --muted: #9aa1ac;
    --border: #30343c;
    --accent: #59c98a;
    --accent-hover: #3aae72;
    --ok: #4fd17c;
    --ok-bg: #10301c;
    --bad: #ff8a80;
    --bad-bg: #3a1614;
    --code-bg: #262a32;
    --link: #59c98a;
  }
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  padding-bottom: 4rem;
}
a { color: var(--link); }

.container {
  max-width: 880px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

header.site-header {
  border-bottom: 1px solid var(--border);
  background: var(--panel);
  padding: 0.9rem 0;
  margin-bottom: 2rem;
}
header.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 0.5rem;
}
header.site-header .brand {
  font-weight: 700;
  font-size: 1.05rem;
  text-decoration: none;
  color: var(--text);
}
header.site-header nav {
  display: flex;
  gap: 1.1rem;
  flex-wrap: wrap;
}
header.site-header nav a {
  text-decoration: none;
  color: var(--muted);
  font-size: 0.92rem;
}
header.site-header nav a:hover,
header.site-header nav a.active {
  color: var(--accent);
  font-weight: 600;
}

h1 { font-size: 1.6rem; margin: 0 0 0.4rem; }
h2 { font-size: 1.2rem; margin: 2rem 0 0.6rem; }
h3 { font-size: 1.02rem; margin: 1.2rem 0 0.4rem; }
p.lead { color: var(--muted); margin-top: 0; }

.card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.2rem 1.3rem;
  margin-bottom: 1.4rem;
}

.mode-toggle {
  display: inline-flex;
  border: 1px solid var(--accent);
  border-radius: 999px;
  padding: 3px;
  background: transparent;
  margin-bottom: 1rem;
}
.mode-toggle button {
  border: none;
  background: transparent;
  padding: 0.4rem 1rem;
  border-radius: 999px;
  cursor: pointer;
  font-size: 0.9rem;
  color: var(--accent);
}
.mode-toggle button:hover,
.mode-toggle button.active {
  background: var(--accent);
  color: white;
}

label.field-label {
  display: block;
  font-size: 0.85rem;
  color: var(--muted);
  margin-bottom: 0.3rem;
}

input[type=text], textarea, select {
  width: 100%;
  font-size: 1rem;
  padding: 0.55rem 0.7rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--panel);
  color: var(--text);
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
}
textarea { font-family: inherit; }

.symbol-palette {
  display: flex;
  gap: 0.35rem;
  margin: 0.5rem 0 0.9rem;
  flex-wrap: wrap;
}
.symbol-palette button {
  min-width: 2.1rem;
  padding: 0.3rem 0.5rem;
  border: 1px solid var(--accent);
  border-radius: 6px;
  background: var(--accent);
  color: white;
  cursor: pointer;
  font-size: 1.05rem;
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
}
.symbol-palette button:hover { background: var(--accent-hover); border-color: var(--accent-hover); }
.palette-break { display: none; }

button.btn {
  background: var(--accent);
  color: white;
  border: 1px solid var(--accent);
  padding: 0.55rem 1.1rem;
  border-radius: 8px;
  font-size: 0.95rem;
  cursor: pointer;
  margin-right: 0.5rem;
}
button.btn:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
}
button.btn.secondary {
  background: var(--accent);
  color: white;
  border: 1px solid var(--accent);
}
button.btn.secondary:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
}
button.btn.danger { background: var(--bad); border-color: var(--bad); }
button.btn.small { padding: 0.26rem 0.62rem; font-size: 0.82rem; }

.msg { padding: 0.7rem 0.9rem; border-radius: 8px; margin: 0.7rem 0; font-size: 0.92rem; }
.msg.ok { background: var(--ok-bg); color: var(--ok); }
.msg.bad { background: var(--bad-bg); color: var(--bad); }
.msg.info { background: var(--code-bg); color: var(--muted); }

table.truth-table {
  border-collapse: collapse;
  width: 100%;
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
  font-size: 0.95rem;
}
table.truth-table th, table.truth-table td {
  border: 1px solid var(--border);
  padding: 0.4rem 0.6rem;
  text-align: center;
}
table.truth-table th { background: var(--code-bg); }
table.truth-table td.main-col { font-weight: 600; }
table.truth-table tr.counter-row { background: var(--bad-bg); }

.badge {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 600;
}
.badge.tautology { background: var(--ok-bg); color: var(--ok); }
.badge.contradiction { background: var(--bad-bg); color: var(--bad); }
.badge.contingency { background: var(--code-bg); color: var(--muted); }

.proof-line {
  display: grid;
  grid-template-columns: 2.4rem 1fr auto auto;
  gap: 0.5rem;
  align-items: start;
  padding: 0.35rem 0.2rem;
  border-bottom: 1px dashed var(--border);
}
.proof-line .lineno { color: var(--muted); font-size: 0.85rem; padding-top: 0.5rem; }
.proof-line .formula-display {
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
  font-size: 1.05rem;
  padding-top: 0.45rem;
}
.proof-box {
  border-left: 2px solid var(--muted);
  margin-left: 1.1rem;
  padding-left: 0.8rem;
  margin-bottom: 0.4rem;
}
.proof-box .assumption { border-bottom: 1px solid var(--muted); margin-bottom: 0.2rem; }

.tree-node { font-family: "Cambria Math", "STIX Two Math", Georgia, serif; }
ul.tree-list { list-style: none; padding-left: 1.1rem; margin: 0.15rem 0; border-left: 1px dotted var(--border); }
ul.tree-list.root { border-left: none; padding-left: 0; }
ul.tree-list li { position: relative; padding: 0.1rem 0 0.1rem 0.4rem; }
.tree-closed { color: var(--bad); font-weight: 600; }
.tree-open { color: var(--ok); font-weight: 600; }

footer.site-footer {
  margin-top: 3rem;
  padding-top: 1.2rem;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.85rem;
}

#single-table-wrap, #arg-table-wrap { overflow-x: auto; }
.rule-select { max-width: 220px; display: inline-block; }
.cites-input { max-width: 140px; display: inline-block; }

.tool-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
  margin-top: 1.5rem;
}
.tool-card {
  display: block;
  text-decoration: none;
  color: inherit;
  margin-bottom: 0;
  border: 2px solid var(--accent);
  border-top: 5px solid var(--accent);
  transition: transform 0.15s ease, background 0.15s ease, box-shadow 0.15s ease;
}
.tool-card:hover {
  transform: translateY(-2px);
  background: var(--ok-bg);
  box-shadow: 0 6px 18px rgba(0, 0, 0, 0.06);
}
.tool-card h3 { margin-top: 0; color: var(--accent); }
.tool-card p { color: var(--muted); font-size: 0.9rem; margin-bottom: 0; }

.tips-list {
  margin: 0.5rem 0 0;
  padding-left: 1.25rem;
}
.tips-list li {
  margin: 0.45rem 0;
  padding-left: 0.2rem;
}
.tip-conversions {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.35rem 0.9rem;
  margin-top: 0.45rem;
}
.tip-conversion {
  white-space: nowrap;
  font-size: 0.9rem;
}
.tip-conversion strong {
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
  font-size: 1.05rem;
}
.help-text { color: var(--muted); font-size: 0.85rem; }
code { background: var(--code-bg); padding: 0.1rem 0.35rem; border-radius: 4px; }

.rule-help-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.45rem 0.7rem;
}
.rule-help-item {
  display: grid;
  grid-template-columns: max-content 1fr;
  gap: 0.55rem;
  align-items: center;
  min-width: 0;
  padding: 0.42rem 0.55rem;
  border: 1px solid var(--border);
  border-radius: 7px;
  background: var(--panel);
  font-size: 0.82rem;
  overflow-x: auto;
  white-space: nowrap;
}
.rule-help-item strong {
  color: var(--accent);
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
}

@media (max-width: 640px) {
  .proof-line { grid-template-columns: 2rem 1fr; }
  .proof-line .lineno { grid-row: 1; }
  .tool-grid { grid-template-columns: 1fr; }
  .tip-conversions { grid-template-columns: 1fr; }
  .rule-help-grid { grid-template-columns: 1fr; }
  .symbol-palette {
    gap: 0.22rem;
  }
  .symbol-palette button {
    min-width: 1.82rem;
    padding: 0.22rem 0.36rem;
    font-size: 0.98rem;
  }
  .symbol-palette .palette-break {
    display: block;
    flex-basis: 100%;
    width: 0;
    height: 0;
  }
  button.btn.small {
    padding: 0.23rem 0.56rem;
    font-size: 0.8rem;
  }
}