:root{
  --bg: #f6f7fb;
  --panel: #ffffff;
  --text: #111827;
  --muted: #6b7280;
  --border: rgba(17,24,39,.12);
  --shadow: 0 12px 30px rgba(17,24,39,.08);
  --shadow2: 0 8px 20px rgba(17,24,39,.08);
  --primary: #2563eb;
  --primary2: #1d4ed8;
  --danger: #dc2626;
  --ok: #059669;
  --chip: rgba(37,99,235,.10);
  --chipText: #1d4ed8;
  --ring: rgba(37,99,235,.28);
  --kbd: rgba(17,24,39,.04);
  --cardSoft: rgba(17,24,39,.03);
  --canvasGrid: rgba(17,24,39,.08);
}

[data-theme="dark"]{
  --bg: #0b1220;
  --panel: #0f172a;
  --text: #e5e7eb;
  --muted: #9ca3af;
  --border: rgba(229,231,235,.12);
  --shadow: 0 12px 30px rgba(0,0,0,.40);
  --shadow2: 0 8px 20px rgba(0,0,0,.35);
  --primary: #60a5fa;
  --primary2: #3b82f6;
  --danger: #f87171;
  --ok: #34d399;
  --chip: rgba(96,165,250,.12);
  --chipText: #93c5fd;
  --ring: rgba(96,165,250,.25);
  --kbd: rgba(229,231,235,.05);
  --cardSoft: rgba(229,231,235,.04);
  --canvasGrid: rgba(229,231,235,.10);
}

*{ box-sizing: border-box; }
html, body{ height: 100%; }
body{
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Arial, "Apple Color Emoji","Segoe UI Emoji";
  background: radial-gradient(1200px 800px at 20% -10%, rgba(37,99,235,.12), transparent 50%),
              radial-gradient(1000px 600px at 100% 0%, rgba(5,150,105,.10), transparent 45%),
              var(--bg);
  color: var(--text);
}

code{
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  font-size: .95em;
}

.app{
  min-height: 100%;
  display: flex;
  flex-direction: column;
}

.topbar{
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(255,255,255,.65);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
  padding: 14px 18px;
  display: flex;
  align-items: center;
  gap: 14px;
  justify-content: space-between;
}
[data-theme="dark"] .topbar{
  background: rgba(15,23,42,.70);
}

.brand{
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 240px;
}
.logo{
  width: 44px;
  height: 44px;
  border-radius: 14px;
  display:flex;
  align-items:center;
  justify-content:center;
  background: linear-gradient(135deg, rgba(37,99,235,.18), rgba(5,150,105,.14));
  border: 1px solid var(--border);
  box-shadow: var(--shadow2);
  font-weight: 800;
}
.title{
  font-weight: 800;
  letter-spacing: .2px;
}
.subtitle{
  font-size: 12px;
  color: var(--muted);
  margin-top: 2px;
}

.top-actions{
  display:flex;
  align-items:center;
  gap: 10px;
}

.btn{
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  padding: 10px 12px;
  border-radius: 12px;
  cursor: pointer;
  box-shadow: var(--shadow2);
  transition: transform .12s ease, box-shadow .12s ease, background .12s ease, border-color .12s ease;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  user-select: none;
}
.btn:hover{ transform: translateY(-1px); box-shadow: var(--shadow); }
.btn:active{ transform: translateY(0px) scale(.99); }
.btn.ghost{
  background: transparent;
  box-shadow: none;
}
.btn.ghost:hover{
  background: var(--cardSoft);
}
.btn.primary{
  background: var(--primary);
  border-color: rgba(0,0,0,0);
  color: #fff;
}
.btn.primary:hover{ background: var(--primary2); }

.icon{ font-weight: 700; width: 18px; text-align: center; }

.seg{
  display: inline-flex;
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
  background: var(--panel);
  box-shadow: var(--shadow2);
}
.seg-btn{
  padding: 10px 12px;
  border: 0;
  background: transparent;
  color: var(--muted);
  cursor: pointer;
  transition: background .12s ease, color .12s ease;
}
.seg-btn.active{
  background: var(--chip);
  color: var(--chipText);
  font-weight: 700;
}

.tabs{
  display:flex;
  gap: 8px;
  padding: 12px 18px;
  flex-wrap: wrap;
  border-bottom: 1px solid var(--border);
}
.tab{
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  padding: 10px 12px;
  border-radius: 999px;
  cursor: pointer;
  transition: transform .12s ease, background .12s ease, border-color .12s ease;
}
.tab:hover{ transform: translateY(-1px); }
.tab.active{
  background: var(--chip);
  border-color: rgba(37,99,235,.25);
  box-shadow: 0 10px 20px rgba(37,99,235,.08);
  font-weight: 700;
}

.main{
  display: grid;
  grid-template-columns: 1fr 360px;
  gap: 16px;
  padding: 16px 18px 22px;
  max-width: 1320px;
  width: 100%;
  margin: 0 auto;
  flex: 1;
}

.card{
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 18px;
  box-shadow: var(--shadow2);
}
.card.pad{ padding: 14px; }
.card-soft{
  background: var(--cardSoft);
  border: 1px solid var(--border);
  border-radius: 16px;
}

.workspace{
  display:flex;
  flex-direction: column;
  gap: 14px;
}

.screen{
  padding: 14px;
}
.screen-top{
  display:flex;
  align-items:center;
  justify-content: space-between;
  gap: 10px;
}
.pill{
  padding: 8px 10px;
  border-radius: 999px;
  background: rgba(5,150,105,.12);
  color: var(--ok);
  border: 1px solid rgba(5,150,105,.25);
  font-weight: 700;
  font-size: 12px;
}
.mini{
  font-size: 12px;
  color: var(--muted);
  display:flex;
  align-items:center;
  gap: 8px;
}
.dot{ opacity: .6; }
.mini-label{ opacity:.85; }
.mini-value{ font-weight: 700; color: var(--text); opacity:.9; }

.display{
  margin-top: 10px;
  padding: 14px;
  border-radius: 16px;
  background: linear-gradient(180deg, rgba(37,99,235,.08), transparent 70%);
  border: 1px dashed var(--border);
}
.expr{
  min-height: 24px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  color: var(--muted);
  font-size: 14px;
  word-break: break-word;
}
.result{
  margin-top: 8px;
  font-size: 34px;
  font-weight: 900;
  letter-spacing: .3px;
  word-break: break-word;
}

.screen-actions{
  display:flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 12px;
}

.tabpanes{ display:block; }
.pane{ display:none; }
.pane.active{ display:block; }

.grid-2{
  display:grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}

.h3{
  margin: 0 0 8px;
  font-size: 16px;
}
.muted{ color: var(--muted); }
.small{ font-size: 12px; }

.quick-row{
  display:flex;
  gap: 8px;
  flex-wrap: wrap;
  margin: 10px 0 12px;
}
.chip{
  border: 1px solid var(--border);
  background: var(--chip);
  color: var(--chipText);
  border-radius: 999px;
  padding: 8px 10px;
  cursor: pointer;
  transition: transform .12s ease;
  font-weight: 700;
}
.chip:hover{ transform: translateY(-1px); }
.chip:active{ transform: translateY(0px) scale(.99); }

.kbd{ padding: 12px; }
.kbd-grid{
  display:grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}
.key{
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  padding: 14px 10px;
  border-radius: 14px;
  cursor: pointer;
  font-weight: 800;
  transition: transform .12s ease, background .12s ease, box-shadow .12s ease;
  box-shadow: 0 10px 18px rgba(0,0,0,.05);
}
.key:hover{ transform: translateY(-1px); }
.key:active{ transform: translateY(0px) scale(.99); }
.key.op{ background: linear-gradient(180deg, rgba(37,99,235,.10), transparent 65%); }
.key.primary{
  background: var(--primary);
  color: #fff;
  border-color: rgba(0,0,0,0);
}
.key.ghost{
  background: transparent;
  box-shadow: none;
}
.key.ghost:hover{ background: var(--kbd); }

.row{ display:flex; align-items:center; }
.gap{ gap: 10px; margin-top: 12px; flex-wrap: wrap; }

.alert{
  margin-top: 10px;
  padding: 10px 12px;
  border-radius: 14px;
  border: 1px solid rgba(220,38,38,.30);
  background: rgba(220,38,38,.10);
  color: var(--danger);
  font-weight: 700;
}

.steps{
  margin: 10px 0 0;
  width: 100%;
  min-height: 260px;
  border-radius: 16px;
  border: 1px solid var(--border);
  background: var(--kbd);
  padding: 12px;
  overflow: auto;
  white-space: pre-wrap;
  word-break: break-word;
}

.sidebar{
  display:flex;
  flex-direction: column;
  gap: 14px;
}

.history{
  margin-top: 10px;
  display:flex;
  flex-direction: column;
  gap: 10px;
}
.hist-item{
  border: 1px solid var(--border);
  background: var(--panel);
  border-radius: 14px;
  padding: 10px 12px;
  cursor: pointer;
  transition: transform .12s ease, background .12s ease;
}
.hist-item:hover{ transform: translateY(-1px); background: var(--cardSoft); }
.hist-expr{
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  font-size: 12px;
  color: var(--muted);
}
.hist-res{
  margin-top: 6px;
  font-weight: 900;
  font-size: 16px;
}

.list{
  margin: 10px 0 0;
  padding-left: 18px;
  color: var(--muted);
}
.list li{ margin: 6px 0; }

.placeholder{
  display:flex;
  align-items:center;
  gap: 12px;
  padding: 14px;
  border-radius: 16px;
  border: 1px dashed var(--border);
  background: var(--kbd);
  margin-top: 10px;
}
.ph-icon{
  width: 44px;
  height: 44px;
  border-radius: 14px;
  display:flex;
  align-items:center;
  justify-content:center;
  font-weight: 900;
  background: linear-gradient(135deg, rgba(37,99,235,.18), rgba(5,150,105,.12));
  border: 1px solid var(--border);
}
.ph-title{ font-weight: 900; }
.ph-sub{ color: var(--muted); font-size: 12px; margin-top: 2px; }

#graphCanvas{
  width: 100%;
  height: auto;
  border-radius: 16px;
  border: 1px solid var(--border);
  background: rgba(0,0,0,.02);
}

.footer{
  padding: 14px 18px 22px;
  display:flex;
  justify-content:center;
  gap: 10px;
  color: var(--muted);
  font-size: 12px;
}

.hide-sm{ display: inline; }
@media (max-width: 1080px){
  .main{ grid-template-columns: 1fr; }
  .sidebar{ order: 2; }
}
@media (max-width: 720px){
  .grid-2{ grid-template-columns: 1fr; }
  .hide-sm{ display: none; }
  .topbar{ padding: 12px 14px; }
  .tabs{ padding: 10px 14px; }
  .main{ padding: 14px 14px 18px; }
  .result{ font-size: 30px; }
}