/* Single-Path Studio — stylesheet */

:root{
  --bg:#131419; --panel:#1b1d24; --panel2:#22252e; --inset:#0f1014;
  --line:#2e313a; --line2:#3b3f4a;
  --text:#e7e9ee; --muted:#969cab; --dim:#5b5e69;
  --cyan:#37d6c3; --cyan-d:#1c6f66;
  --amber:#f0a93b; --green:#5ec98a; --red:#e8595a;
  --sans:'Space Grotesk',system-ui,sans-serif; --mono:'IBM Plex Mono',ui-monospace,monospace;
}
*{box-sizing:border-box}
html,body{margin:0;height:100%}
body{background:var(--bg);color:var(--text);font-family:var(--sans);font-size:14px;overflow:hidden}
.app{display:grid;grid-template-columns:352px 1fr;height:100vh}

/* ---- control rack ---- */
.rack{background:var(--panel);border-right:1px solid var(--line);overflow-y:auto;padding:0 0 48px}
.rack::-webkit-scrollbar{width:10px}
.rack::-webkit-scrollbar-thumb{background:var(--line2);border-radius:6px}
.brand{padding:18px 20px 14px;border-bottom:1px solid var(--line);position:sticky;top:0;background:var(--panel);z-index:5}
.brand h1{margin:0;font-size:15px;font-weight:600;letter-spacing:.2px}
.brand p{margin:3px 0 0;font-family:var(--mono);font-size:11px;color:var(--muted)}

.mod{border-bottom:1px solid var(--line)}
.mod>summary{list-style:none;cursor:pointer;padding:13px 20px;display:flex;align-items:center;gap:9px;
  font-size:11px;font-weight:600;letter-spacing:.13em;text-transform:uppercase;color:var(--muted);user-select:none}
.mod>summary::-webkit-details-marker{display:none}
.mod>summary::before{content:"";width:6px;height:6px;border-right:1.5px solid var(--muted);border-bottom:1.5px solid var(--muted);
  transform:rotate(-45deg);transition:transform .15s;margin-bottom:2px}
.mod[open]>summary::before{transform:rotate(45deg)}
.mod>summary .tag{margin-left:auto;font-family:var(--mono);font-size:10px;color:var(--cyan);letter-spacing:0;text-transform:none;font-weight:400}
.body{padding:4px 20px 18px}

.row{margin:13px 0}
.row label{display:flex;justify-content:space-between;align-items:baseline;font-size:12px;color:var(--text);margin-bottom:6px}
.row label .v{font-family:var(--mono);font-size:12px;color:var(--cyan)}
.row label .unit{color:var(--dim)}
input[type=range]{-webkit-appearance:none;width:100%;height:3px;background:var(--line2);border-radius:3px;outline:none}
input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;width:14px;height:14px;border-radius:50%;
  background:var(--cyan);cursor:pointer;border:2px solid var(--panel)}
input[type=range]::-moz-range-thumb{width:14px;height:14px;border-radius:50%;background:var(--cyan);cursor:pointer;border:2px solid var(--panel)}
input[type=range]:focus-visible{box-shadow:0 0 0 2px var(--cyan-d)}

.expr label{font-size:12px;color:var(--text);margin-bottom:6px;display:block}
.expr label .fn{font-family:var(--mono);color:var(--muted)}
.expr input[type=text]{width:100%;background:var(--inset);border:1px solid var(--line2);color:var(--text);
  font-family:var(--mono);font-size:12px;padding:8px 10px;border-radius:6px;outline:none}
.expr input[type=text]:focus{border-color:var(--cyan)}
.expr input.bad{border-color:var(--red);color:var(--red)}
.hint{font-family:var(--mono);font-size:10px;color:var(--dim);margin-top:5px}
select{width:100%;background:var(--inset);border:1px solid var(--line2);color:var(--text);
  font-family:var(--mono);font-size:12px;padding:8px 10px;border-radius:6px;outline:none;cursor:pointer;
  -webkit-appearance:none;appearance:none;
  background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6'%3E%3Cpath d='M0 0l5 6 5-6z' fill='%23969cab'/%3E%3C/svg%3E");
  background-repeat:no-repeat;background-position:right 10px center}
select:focus{border-color:var(--cyan)}

.toggle{display:flex;align-items:center;gap:10px;cursor:pointer;font-size:12px;position:relative}
.toggle input{position:absolute;opacity:0}
.sw{width:34px;height:19px;border-radius:11px;background:var(--line2);position:relative;transition:background .15s;flex:none}
.sw::after{content:"";position:absolute;top:2px;left:2px;width:15px;height:15px;border-radius:50%;background:#cfd2d9;transition:transform .15s}
.toggle input:checked + .sw{background:var(--amber)}
.toggle input:checked + .sw::after{transform:translateX(15px)}
.warnote{font-family:var(--mono);font-size:10px;color:var(--amber);margin-top:9px;line-height:1.5;
  border-left:2px solid var(--amber);padding-left:9px}

/* ---- stage ---- */
.stage{display:grid;grid-template-rows:auto 1fr auto;min-width:0}
.formula{background:var(--panel2);border-bottom:1px solid var(--line);padding:14px 22px;overflow-x:auto}
.formula .katex{font-size:1.04em;color:var(--text)}
.formula .l2{margin-top:9px}
.formula .l2 .katex{font-size:.86em}
.formula .l3{margin-top:6px}
.formula .l3 .katex{font-size:.78em;color:var(--muted)}
.viewport{position:relative;min-height:0;overflow:hidden;background:radial-gradient(120% 120% at 50% 18%,#1a1d24 0%,#101116 70%)}
.viewport>canvas{display:block;position:absolute;top:0;left:0}
.vlabel{position:absolute;top:14px;left:16px;font-family:var(--mono);font-size:11px;color:var(--muted);
  pointer-events:none;line-height:1.6}
.vlabel b{color:var(--cyan);font-weight:500}
.vhint{position:absolute;bottom:12px;right:16px;font-family:var(--mono);font-size:10px;color:var(--dim);pointer-events:none}

/* ---- action bar ---- */
.bar{background:var(--panel);border-top:1px solid var(--line);display:flex;align-items:center;gap:10px;padding:10px 14px;flex-wrap:wrap}
.seg{display:flex;border:1px solid var(--line2);border-radius:7px;overflow:hidden}
.seg button{background:transparent;border:none;color:var(--muted);font-family:var(--sans);font-size:12px;
  padding:7px 14px;cursor:pointer}
.seg button.on{background:var(--cyan-d);color:#eafffb}
.lamps{display:flex;gap:16px;margin-left:6px;flex-wrap:wrap}
.lamp{display:flex;align-items:center;gap:7px;font-family:var(--mono);font-size:11px;color:var(--muted)}
.lamp .dot{width:8px;height:8px;border-radius:50%;background:var(--dim);flex:none}
.lamp.ok .dot{background:var(--green)} .lamp.warn .dot{background:var(--amber)} .lamp.fail .dot{background:var(--red)}
.lamp .n{color:var(--text)}
.spacer{flex:1}
.btn{font-family:var(--sans);font-size:12px;font-weight:500;border-radius:7px;padding:7px 12px;cursor:pointer;border:1px solid var(--line2);
  background:var(--panel2);color:var(--text);white-space:nowrap}
.btn:hover{border-color:var(--muted)}
.btn.primary{background:var(--cyan);border-color:var(--cyan);color:#08201d}
.btn.primary:hover{filter:brightness(1.06)}
.btn:focus-visible{outline:2px solid var(--cyan);outline-offset:2px}

/* ---- modal ---- */
.scrim{position:absolute;inset:0;background:rgba(8,9,12,.72);display:none;align-items:center;justify-content:center;z-index:20}
.scrim.show{display:flex}
.modal{width:min(720px,92%);max-height:86%;background:var(--panel);border:1px solid var(--line2);border-radius:12px;
  display:flex;flex-direction:column;overflow:hidden}
.modal header{padding:16px 20px;border-bottom:1px solid var(--line);display:flex;align-items:center}
.modal header h2{margin:0;font-size:15px;font-weight:600}
.modal header .x{margin-left:auto;background:none;border:none;color:var(--muted);font-size:20px;cursor:pointer;line-height:1}
.modal .content{padding:18px 20px;overflow-y:auto}
.statgrid{display:grid;grid-template-columns:repeat(4,1fr);gap:1px;background:var(--line);border:1px solid var(--line);border-radius:8px;overflow:hidden;margin-bottom:16px}
.stat{background:var(--panel2);padding:11px 13px}
.stat .k{font-family:var(--mono);font-size:10px;color:var(--muted);text-transform:uppercase;letter-spacing:.08em}
.stat .val{font-family:var(--mono);font-size:16px;color:var(--cyan);margin-top:3px}
.gpre{background:var(--inset);border:1px solid var(--line);border-radius:8px;font-family:var(--mono);font-size:11px;
  color:var(--muted);padding:12px 14px;max-height:220px;overflow:auto;white-space:pre;line-height:1.55}
.mrow{display:flex;gap:10px;margin-top:16px;flex-wrap:wrap}
.send{margin-top:18px;border-top:1px solid var(--line);padding-top:16px}
.send .lbl{font-size:12px;color:var(--muted);margin-bottom:8px}
.send code{display:block;background:var(--inset);border:1px solid var(--line);border-radius:7px;padding:11px 13px;
  font-family:var(--mono);font-size:11px;color:var(--text);overflow-x:auto;white-space:pre}

/* ---- z-function plots ---- */
.zplot{display:block;width:100%;height:44px;background:var(--inset);border:1px solid var(--line);border-radius:6px;margin-top:6px}

/* ---- viewport controls ---- */
.vcontrols{position:absolute;top:12px;right:14px;display:flex;flex-direction:column;gap:4px;z-index:4}
.vcontrols button{background:var(--panel);border:1px solid var(--line2);color:var(--muted);font-family:var(--mono);font-size:11px;
  padding:5px 10px;border-radius:5px;cursor:pointer;white-space:nowrap;transition:border-color .12s,color .12s}
.vcontrols button:hover{border-color:var(--cyan);color:var(--text)}
.vcontrols button.active{background:var(--cyan-d);color:#eafffb}
.vcontrols button:focus-visible{outline:2px solid var(--cyan);outline-offset:2px}

@media (max-width:880px){
  .app{grid-template-columns:1fr;grid-template-rows:auto 1fr;height:auto;min-height:100vh}
  .rack{max-height:42vh}
  .viewport{min-height:48vh}
  .vcontrols{flex-direction:row;flex-wrap:wrap;top:auto;bottom:48px;right:8px}
}
@media (prefers-reduced-motion:reduce){*{transition:none!important}}

/* ---- expression input wrapper + ƒx edit button ---- */
.expr-input-wrap{position:relative;display:flex;align-items:center}
.expr-input-wrap input[type=text]{flex:1;padding-right:36px}
.expr-edit-btn{position:absolute;right:4px;top:50%;transform:translateY(-50%);
  background:var(--panel2);border:1px solid var(--line2);color:var(--muted);
  font-family:var(--mono);font-size:11px;font-weight:600;
  padding:3px 7px;border-radius:4px;cursor:pointer;
  transition:all .18s ease;line-height:1;letter-spacing:.02em}
.expr-edit-btn:hover{border-color:var(--cyan);color:var(--cyan);
  box-shadow:0 0 8px rgba(55,214,195,.25)}
.expr-edit-btn:active{transform:translateY(-50%) scale(.93)}

/* ---- formula editor overlay ---- */
.fe-overlay{position:fixed;inset:0;background:rgba(8,9,14,.78);
  backdrop-filter:blur(8px);-webkit-backdrop-filter:blur(8px);
  display:none;align-items:center;justify-content:center;z-index:100;
  opacity:0;transition:opacity .2s ease}
.fe-overlay.open{display:flex;opacity:1}

/* ---- formula editor dialog ---- */
.fe-dialog{width:min(680px,94vw);max-height:min(92vh,860px);
  background:linear-gradient(168deg,rgba(30,33,42,.97) 0%,rgba(22,24,32,.99) 100%);
  border:1px solid var(--line2);border-radius:14px;
  box-shadow:0 24px 80px rgba(0,0,0,.55),0 0 1px rgba(55,214,195,.15);
  display:flex;flex-direction:column;overflow:hidden;
  animation:feSlideIn .22s ease-out}
@keyframes feSlideIn{from{opacity:0;transform:translateY(16px) scale(.97)}to{opacity:1;transform:translateY(0) scale(1)}}

/* header */
.fe-header{display:flex;align-items:center;padding:16px 20px;border-bottom:1px solid var(--line);flex:none}
.fe-title{display:flex;align-items:center;gap:10px;flex:1;min-width:0}
.fe-icon{font-family:var(--mono);font-size:16px;font-weight:700;color:var(--cyan);
  background:rgba(55,214,195,.1);border:1px solid rgba(55,214,195,.2);
  padding:4px 8px;border-radius:6px;line-height:1}
.fe-header h2{margin:0;font-size:15px;font-weight:600;color:var(--text);white-space:nowrap}
.fe-field-name{font-family:var(--mono);font-size:12px;color:var(--muted);
  overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.fe-close{background:none;border:none;color:var(--muted);font-size:22px;cursor:pointer;
  padding:4px 8px;border-radius:6px;line-height:1;transition:color .12s,background .12s}
.fe-close:hover{color:var(--text);background:rgba(255,255,255,.06)}

/* body */
.fe-body{flex:1;overflow-y:auto;padding:18px 20px 12px;display:flex;flex-direction:column;gap:16px}

/* formula input section */
.fe-input-section{display:flex;flex-direction:column;gap:6px}
.fe-label{font-size:12px;font-weight:500;color:var(--muted);letter-spacing:.04em;text-transform:uppercase}
.fe-input{width:100%;background:var(--inset);border:1px solid var(--line2);color:var(--text);
  font-family:var(--mono);font-size:14px;padding:12px 14px;border-radius:8px;outline:none;
  transition:border-color .15s,box-shadow .15s}
.fe-input:focus{border-color:var(--cyan);box-shadow:0 0 0 3px rgba(55,214,195,.12)}
.fe-input.invalid{border-color:var(--red);box-shadow:0 0 0 3px rgba(232,89,90,.1)}
.fe-error{font-family:var(--mono);font-size:11px;color:var(--red);min-height:16px;
  padding-left:2px;transition:opacity .15s;opacity:0}
.fe-error.show{opacity:1}

/* palette */
.fe-palette{display:flex;flex-direction:column;gap:10px}
.fe-group{display:flex;flex-direction:column;gap:5px}
.fe-group-label{font-size:10px;font-weight:600;color:var(--dim);letter-spacing:.1em;text-transform:uppercase}
.fe-btn-row{display:flex;flex-wrap:wrap;gap:5px}

/* function buttons — base */
.fe-fn-btn{font-family:var(--mono);font-size:12px;font-weight:500;
  padding:7px 12px;border-radius:6px;cursor:pointer;
  border:1px solid var(--line2);background:var(--panel2);color:var(--text);
  transition:all .14s ease;line-height:1;white-space:nowrap}
.fe-fn-btn:hover{border-color:var(--cyan);color:var(--cyan);
  background:rgba(55,214,195,.06);box-shadow:0 0 10px rgba(55,214,195,.12)}
.fe-fn-btn:active{transform:scale(.93);transition-duration:.06s}

/* two-arg function buttons — amber accent */
.fe-fn-btn.fn2{border-color:rgba(240,169,59,.2);color:var(--amber)}
.fe-fn-btn.fn2:hover{border-color:var(--amber);background:rgba(240,169,59,.08);
  box-shadow:0 0 10px rgba(240,169,59,.12);color:var(--amber)}

/* variable buttons — green accent */
.fe-fn-btn.var{border-color:rgba(94,201,138,.2);color:var(--green);font-weight:600}
.fe-fn-btn.var:hover{border-color:var(--green);background:rgba(94,201,138,.08);
  box-shadow:0 0 10px rgba(94,201,138,.12)}

/* operator buttons — subtle */
.fe-fn-btn.op{font-size:14px;font-weight:600;min-width:36px;text-align:center;
  color:var(--muted);padding:7px 10px}
.fe-fn-btn.op:hover{border-color:var(--muted);color:var(--text);background:rgba(255,255,255,.04)}

/* graph section */
.fe-graph-section{position:relative}
.fe-graph-label{font-size:10px;font-weight:600;color:var(--dim);letter-spacing:.1em;
  text-transform:uppercase;margin-bottom:6px;display:flex;align-items:baseline;gap:8px}
.fe-graph-range{font-weight:400;letter-spacing:0;text-transform:none;color:var(--muted);font-family:var(--mono)}
.fe-graph{display:block;width:100%;height:240px;background:var(--inset);
  border:1px solid var(--line);border-radius:8px;cursor:crosshair}
.fe-crosshair{position:absolute;bottom:8px;right:12px;font-family:var(--mono);font-size:11px;
  color:var(--cyan);pointer-events:none;opacity:0;transition:opacity .12s}
.fe-crosshair.show{opacity:1}

/* action footer */
.fe-actions{display:flex;justify-content:flex-end;gap:10px;padding:14px 20px;
  border-top:1px solid var(--line);flex:none}
.fe-btn-cancel{font-family:var(--sans);font-size:13px;font-weight:500;
  padding:9px 20px;border-radius:8px;cursor:pointer;
  border:1px solid var(--line2);background:transparent;color:var(--muted);
  transition:all .14s ease}
.fe-btn-cancel:hover{border-color:var(--muted);color:var(--text)}
.fe-btn-apply{font-family:var(--sans);font-size:13px;font-weight:600;
  padding:9px 24px;border-radius:8px;cursor:pointer;
  border:1px solid var(--cyan);background:var(--cyan);color:#08201d;
  transition:all .14s ease}
.fe-btn-apply:hover{filter:brightness(1.08);box-shadow:0 0 14px rgba(55,214,195,.3)}
.fe-btn-apply:disabled{opacity:.4;cursor:not-allowed;filter:none;box-shadow:none}