:root{
  --bg:#f2f1ec;
  --paper:#ffffff;
  --ink:#23262b;
  --muted:#8e887c;
  --line:#e5e1d7;
  --accent:#1f6f5c;
  --accent-soft:#e8f1ee;
  --font-sans:"Inter","Segoe UI","PingFang SC","Microsoft YaHei",system-ui,sans-serif;
  --font-mono:"JetBrains Mono","Cascadia Mono",Consolas,monospace;
}
*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;
  display:flex;
  flex-direction:column;
  overflow:hidden;
  background:var(--bg);
  color:var(--ink);
  font-family:var(--font-sans);
  -webkit-font-smoothing:antialiased;
  user-select:none;
}

/* ---------- toolbar ---------- */
.toolbar{
  flex:0 0 auto;
  display:flex;
  flex-wrap:wrap;
  align-items:center;
  gap:14px;
  padding:11px 18px;
  background:#fff;
  border-bottom:1px solid var(--line);
  position:relative;
  z-index:3;
}
.brand{display:flex;align-items:center;gap:9px;flex:0 0 auto}
.brand svg{width:22px;height:22px;color:var(--accent);flex:0 0 auto}
.brand h1{margin:0;font-size:14.5px;font-weight:600;letter-spacing:.02em}
.brand p{margin:2px 0 0;font-family:var(--font-mono);font-size:8px;letter-spacing:.18em;color:#a49d90}
.group{display:flex;align-items:center;gap:8px;min-width:0}
.group-label{font-size:10px;letter-spacing:.1em;color:#a49d90;flex:0 0 auto}
.elements,.orders{display:flex;flex-wrap:wrap;gap:4px}
.template-list{display:flex;flex-wrap:wrap;gap:4px}
.tpl{
  height:32px;padding:0 8px;
  display:inline-flex;align-items:center;justify-content:center;
  border:1px solid var(--line);border-radius:8px;
  background:#fff;color:#3c3f45;
  font-family:var(--font-sans);font-size:11.5px;font-weight:500;
  cursor:pointer;transition:.15s;
}
.tpl:hover{background:var(--accent-soft);border-color:var(--accent-line);color:var(--accent-ink)}
.tpl:active{transform:translateY(1px)}
.element,.order{
  height:32px;min-width:34px;padding:0 7px;
  display:inline-flex;align-items:center;justify-content:center;
  border:1px solid var(--line);border-radius:8px;
  background:#fff;color:#3c3f45;
  font-family:var(--font-sans);font-size:12.5px;font-weight:600;
  cursor:pointer;transition:background .15s,border-color .15s,color .15s,box-shadow .15s;
}
.element:hover,.order:hover{border-color:#c9c2b4;background:#faf9f6}
.element[aria-pressed="true"]{
  background:var(--ink);border-color:var(--ink);color:#fff;
  box-shadow:0 1px 2px rgba(35,38,43,.2);
}
.order{font-weight:500;font-size:11.5px;color:#6d6a62}
.order[aria-pressed="true"]{
  background:var(--accent-soft);border-color:#9ec4b9;color:var(--accent);font-weight:600;
}
.divider{width:1px;height:24px;background:var(--line);flex:0 0 auto}
.actions{margin-left:auto;display:flex;gap:8px;flex:0 0 auto}
.btn{
  height:33px;padding:0 14px;
  border:1px solid var(--line);border-radius:8px;
  background:#fff;color:#3c3f45;
  font-family:var(--font-sans);font-size:12.5px;font-weight:500;
  cursor:pointer;transition:.15s;
}
.btn:hover{border-color:#c9c2b4;background:#faf9f6}
.btn.primary{
  background:var(--accent);border-color:var(--accent);color:#fff;
  box-shadow:0 1px 2px rgba(31,111,92,.25);
}
.btn.primary:hover{background:#195c4c;border-color:#195c4c}
.btn[aria-pressed="true"]{
  background:var(--accent-soft);border-color:#9ec4b9;color:var(--accent);font-weight:600;
}
.btn[aria-pressed="true"]:hover{background:#dcebe6;border-color:#8bbcae}
.btn:disabled{
  opacity:.35;cursor:not-allowed;background:#fff;border-color:var(--line);
  color:#3c3f45;box-shadow:none;
}
.btn:disabled:hover{background:#fff;border-color:var(--line)}
.periodic-btn{
  height:32px;padding:0 9px;margin-left:2px;
  display:inline-flex;align-items:center;gap:5px;
  border:1px solid var(--line);border-radius:8px;background:#fff;color:#3c3f45;
  font-family:var(--font-sans);font-size:11.5px;font-weight:500;
  cursor:pointer;transition:.15s;
  flex:0 0 auto;white-space:nowrap;
}
.periodic-btn svg{width:13px;height:13px;opacity:.7;flex:0 0 auto}
.periodic-btn:hover{border-color:#c9c2b4;background:#faf9f6}
.periodic-btn.custom{border-color:#9ec4b9;color:var(--accent);background:var(--accent-soft)}
.periodic-btn:focus-visible{outline:2px solid #9ec4b9;outline-offset:2px}
.btn:focus-visible,.element:focus-visible,.order:focus-visible{
  outline:2px solid #9ec4b9;outline-offset:2px;
}

/* ---------- board ---------- */
.stage{
  flex:1 1 auto;min-height:0;
  display:flex;flex-direction:column;gap:8px;
  padding:16px 18px 10px;
}
.paper{
  position:relative;flex:1 1 auto;min-height:180px;
  border:1px solid #e3dfd5;border-radius:12px;overflow:hidden;
  background-color:#fff;
  background-image:radial-gradient(circle,#dedad0 1px,transparent 1.25px);
  background-size:20px 20px;
  box-shadow:0 1px 2px rgba(40,35,20,.04),0 14px 36px rgba(40,35,20,.06);
}
#board{
  position:absolute;inset:0;width:100%;height:100%;display:block;
  touch-action:none;cursor:crosshair;
}
.hint{margin:0;text-align:center;font-size:11px;line-height:1.5;color:#928b7f;letter-spacing:.01em}
.hint b{font-weight:500;color:#6d675c}
.hint.active{color:var(--accent)}
.hint.active b{color:var(--accent)}

.empty{
  position:absolute;inset:0;z-index:1;
  display:flex;flex-direction:column;align-items:center;justify-content:center;gap:9px;
  pointer-events:none;color:#a8a194;
  transition:opacity .2s ease;
}
.empty.hide{opacity:0}
.empty-icon{
  width:38px;height:38px;border:1px dashed #cbc5b8;border-radius:50%;
  display:grid;place-items:center;
  font-size:20px;font-weight:400;color:#b3ab9d;line-height:1;
}
.empty p{margin:0;font-size:13px;color:#8f887b}
.empty small{font-size:10.5px;color:#b0a99c}

.toast{
  position:fixed;left:50%;bottom:26px;z-index:20;
  transform:translate(-50%,8px);
  background:#23262b;color:#fff;
  font-size:12px;padding:8px 14px;border-radius:999px;
  max-width:min(92vw,560px);text-align:center;line-height:1.45;
  opacity:0;pointer-events:none;transition:.2s ease;
  box-shadow:0 8px 24px rgba(0,0,0,.18);
}
.toast.show{opacity:1;transform:translate(-50%,0)}
.toast.error{background:#7a2b25;border-radius:12px;padding:10px 16px}

/* ---------- element modal ---------- */
.modal{position:fixed;inset:0;z-index:60;display:flex;align-items:center;justify-content:center;padding:18px}
.modal[hidden]{display:none}
.modal-backdrop{position:absolute;inset:0;background:rgba(26,28,24,.42);backdrop-filter:blur(3px);-webkit-backdrop-filter:blur(3px)}
.modal-panel{
  position:relative;display:flex;flex-direction:column;
  width:min(1100px,96vw);max-height:92vh;
  background:#fff;border-radius:14px;overflow:hidden;
  box-shadow:0 30px 90px rgba(20,20,15,.3),0 2px 8px rgba(20,20,15,.1);
  animation:modalIn .18s ease;
}
@keyframes modalIn{from{opacity:0;transform:translateY(6px) scale(.995)}to{opacity:1;transform:none}}
.modal-head{display:flex;align-items:flex-start;justify-content:space-between;gap:12px;padding:15px 18px 6px}
.modal-head h2{margin:0;font-size:15px;font-weight:600;letter-spacing:.01em}
.modal-head p{margin:3px 0 0;font-size:10.5px;color:#928b7f}
.modal-close{
  width:28px;height:28px;flex:0 0 auto;
  border:1px solid var(--line);border-radius:8px;background:#fff;
  color:#6d675c;font-size:18px;line-height:1;cursor:pointer;transition:.15s;
}
.modal-close:hover{background:#faf9f6;border-color:#c9c2b4;color:#23262b}
.modal-close:focus-visible{outline:2px solid #9ec4b9;outline-offset:2px}
.pt-legend{display:flex;flex-wrap:wrap;align-items:center;gap:5px 12px;padding:0 18px 9px;font-size:9.5px;color:#8b8478}
.pt-legend span{display:inline-flex;align-items:center;gap:5px}
.pt-legend i{width:9px;height:9px;border-radius:2px;display:inline-block}
.pt-legend i[data-cat="nonmetal"]{background:#dcefe4}
.pt-legend i[data-cat="halogen"]{background:#edf2d6}
.pt-legend i[data-cat="metalloid"]{background:#f8ead4}
.pt-legend i[data-cat="metal"]{background:#dfe7ee}
.pt-legend i[data-cat="noble"]{background:#ebe4f4}
.pt-legend-note{margin-left:auto;color:#b0a99c;font-size:9px}
.ptable-wrap{overflow:auto;padding:2px 14px 8px;flex:1 1 auto;min-height:0;overscroll-behavior:contain}
.ptable{
  display:grid;
  grid-template-columns:24px repeat(18,minmax(42px,1fr));
  grid-template-rows:20px repeat(7,44px) 8px 40px 40px;
  gap:3px;min-width:840px;
}
.pt-group,.pt-period,.pt-f-label{
  display:flex;align-items:center;justify-content:center;
  font-family:var(--font-mono);font-size:8px;color:#b0a99c;letter-spacing:.02em;
}
.pt-f-label{font-size:9px;color:#928b7f;justify-content:flex-start;padding-left:2px}
.pt-cell{
  position:relative;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:1px;
  border:1px solid transparent;border-radius:6px;padding:1px 2px;overflow:hidden;
  font-family:var(--font-sans);cursor:pointer;
  transition:border-color .12s,box-shadow .12s,transform .12s;
  background:#f6f5f1;color:#23262b;
}
.pt-cell[data-cat="nonmetal"]{background:#e6f3ec}
.pt-cell[data-cat="halogen"]{background:#eef3dc}
.pt-cell[data-cat="metalloid"]{background:#faeddc}
.pt-cell[data-cat="metal"]{background:#e7edf3}
.pt-cell[data-cat="noble"]{background:#efe9f7}
.pt-cell:hover{border-color:#8bbcae;box-shadow:0 3px 10px rgba(30,50,40,.1);transform:translateY(-1px);z-index:1}
.pt-cell:focus-visible{outline:2px solid #9ec4b9;outline-offset:1px;z-index:2}
.pt-cell.current{border-color:var(--accent);box-shadow:inset 0 0 0 1px var(--accent);z-index:1}
.pt-num{position:absolute;top:2px;left:4px;font-family:var(--font-mono);font-size:6.5px;line-height:1;color:#8d867a}
.pt-sym{font-size:13px;font-weight:700;line-height:1;margin-top:1px;letter-spacing:.01em}
.pt-name{font-size:7.5px;line-height:1;color:#6d675c;white-space:nowrap}
.pt-cell.disabled{background:#f7f6f2;color:#b9b2a5;cursor:not-allowed;border-color:#f0eee7}
.pt-cell.disabled:hover{transform:none;border-color:#f0eee7;box-shadow:none}
.pt-cell.disabled .pt-sym{font-weight:500;color:#b9b2a5}
.pt-cell.disabled .pt-num{color:#c5beb1}
.modal-foot{
  display:flex;flex-wrap:wrap;align-items:baseline;gap:3px 14px;
  padding:9px 18px 11px;border-top:1px solid var(--line);
  font-size:10.5px;color:#8b8478;min-height:38px;
}
.modal-foot b{font-weight:600;color:#23262b;font-size:11.5px}
.modal-foot span::before{content:'·';margin-right:7px;color:#c9c2b4}
.only-mobile{display:none}

/* ---------- responsive ---------- */
@media (max-width:900px){
  .toolbar{gap:10px 12px;padding:10px 12px}
  .brand p{display:none}
  .divider{display:none}
  .group-label{display:none}
  .actions{margin-left:0}
  .stage{padding:12px 12px 8px}
}
@media (max-width:620px){
  .brand h1{font-size:13px}
  .brand svg{width:19px;height:19px}
  .element,.order{height:30px;font-size:11.5px}
  .element{min-width:28px;padding:0 4px}
  .order{min-width:30px;padding:0 6px}
  .elements{gap:3px}
  .tpl{height:30px;padding:0 6px;font-size:11px}
  .template-list{gap:3px}
  .btn{height:31px;padding:0 11px;font-size:11.5px}
  .periodic-btn{width:30px;height:30px;padding:0;justify-content:center;gap:0}
  .periodic-btn span{display:none}
  .periodic-btn svg{width:15px;height:15px}
  .periodic-btn.custom svg{display:none}
  .periodic-btn.custom::before{content:attr(data-symbol);font-size:11.5px;font-weight:600;line-height:1}
  .hint{font-size:10px}
  .empty p{font-size:12px}
  .modal{padding:8px}
  .modal-panel{width:96vw;max-height:94vh;border-radius:12px}
  .modal-head{padding:12px 12px 4px}
  .modal-head h2{font-size:14px}
  .pt-legend{padding:0 12px 7px;gap:4px 9px;font-size:9px}
  .pt-legend-note{display:none}
  .ptable-wrap{padding:0 8px 6px}
  .ptable{grid-template-columns:20px repeat(18,minmax(40px,1fr));min-width:760px}
  .modal-foot{padding:8px 12px;font-size:9.5px;gap:2px 10px}
  .modal-foot b{font-size:10.5px}
  .only-mobile{display:inline}
}