:root{
  --bg:#f7f5fd;
  --bg-grad:#f0e9fc;
  --surface:#ffffff;
  --surface-alt:#faf7fe;
  --border:#e7ddf7;
  --border-strong:#d3c0f0;
  --text:#1e1533;
  --muted:#6b6485;
  --accent:#7c3aed;
  --accent-dark:#5b21b6;
  --accent-soft:#f1e8fe;
  --grad-a:#4f46e5;
  --grad-b:#a855f7;
  --grad-c:#ec4899;
  --gradient:linear-gradient(135deg,var(--grad-a),var(--grad-b) 55%,var(--grad-c));
  --warm:#e08a3e;
  --warm-soft:#fbe6d2;
  --pos:#e11d67;
  --neg:#4f46e5;
  --green:#0d9488;
  --success:#0f6b45;
  --success-soft:#e8f6ef;
  --success-border:#b9e5cf;
  --error:#8a2c22;
  --error-soft:#fdecea;
  --error-border:#f3c2bc;
  --shadow-sm:0 2px 10px rgba(76,29,149,0.07);
  --shadow-md:0 12px 30px rgba(76,29,149,0.14);
  --shadow-lg:0 20px 48px rgba(76,29,149,0.18);
  --ease-out-back:cubic-bezier(.34,1.56,.64,1);
  --ease-out:cubic-bezier(.16,1,.3,1);
}
*{box-sizing:border-box}
body{
  margin:0;
  background:
    radial-gradient(1100px 500px at 12% -10%, var(--bg-grad), transparent),
    radial-gradient(900px 500px at 105% 5%, #fdeafc, transparent),
    var(--bg);
  color:var(--text);
  font-family:'Plus Jakarta Sans',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;
  line-height:1.6;
  min-height:100vh;
}
a{color:inherit;text-decoration:none}
h1,h2,h3,h4{font-family:'Space Grotesk',-apple-system,sans-serif;font-weight:600;letter-spacing:-0.015em;color:var(--text)}
code,.mono,.readout,.val,.num-input{font-family:'JetBrains Mono',ui-monospace,Menlo,Consolas,monospace}
.gradient-text{background:var(--gradient);-webkit-background-clip:text;background-clip:text;color:transparent}

/* ---------- Nav ---------- */
nav{
  display:flex;align-items:center;justify-content:space-between;
  padding:18px 32px;
  background:rgba(255,255,255,0.7);
  backdrop-filter:blur(10px);
  border-bottom:1px solid var(--border);
  position:sticky;top:0;z-index:20;
}
.brand{
  font-family:'Orbitron',sans-serif;font-weight:700;font-size:18px;
  letter-spacing:0.04em;text-transform:uppercase;display:inline-block;
  transition:opacity .18s;
}
.brand:hover{opacity:.85}
.brand span{background:var(--gradient);-webkit-background-clip:text;background-clip:text;color:transparent}
.nav-links{display:flex;gap:28px;font-size:14px;color:var(--muted);font-weight:500}
.nav-links a{position:relative;padding-bottom:2px;transition:color .2s}
.nav-links a:hover{color:var(--accent)}
.nav-links a.active{color:var(--accent-dark);font-weight:700}
.nav-links a.active:after{content:'';position:absolute;left:0;right:0;bottom:-4px;height:2px;background:var(--gradient);border-radius:2px}

/* ---------- Nav right cluster: theme toggle + progress/profile chip ---------- */
.nav-right{display:flex;align-items:center;gap:14px}
.nav-progress-chip{
  display:flex;align-items:center;gap:8px;padding:5px 12px 5px 5px;border-radius:999px;
  border:1px solid var(--border-strong);background:var(--surface);transition:all .18s var(--ease-out);
  text-decoration:none;
}
.nav-progress-chip:hover{border-color:var(--accent);background:var(--accent-soft);transform:translateY(-1px)}
.nav-avatar{
  width:26px;height:26px;border-radius:50%;display:flex;align-items:center;justify-content:center;
  color:#fff;font-size:11px;font-weight:700;font-family:'Space Grotesk',sans-serif;flex-shrink:0;
}
.nav-avatar-custom{background:none}
.nav-avatar-custom svg{display:block}
.nav-progress-points{font-size:13px;font-weight:700;color:var(--text);font-family:'JetBrains Mono',monospace}
.nav-progress-pts-label{font-size:10.5px;font-weight:500;color:var(--muted);margin-left:3px;font-family:'Plus Jakarta Sans',sans-serif}
.nav-signin-link{
  font-size:13.5px;font-weight:700;color:#fff;background:var(--accent);
  padding:8px 16px;border-radius:999px;text-decoration:none;transition:all .18s var(--ease-out);
}
.nav-signin-link:hover{background:var(--accent-dark);transform:translateY(-1px)}

/* ---------- Guest notice: usable without an account, but says so ---------- */
.guest-notice{
  margin-top:14px;padding:10px 16px;background:var(--warm-soft);border:1px solid var(--border-strong);
  border-radius:10px;font-size:13px;color:var(--text);
}
.guest-notice a{color:var(--accent-dark);font-weight:700;text-decoration:none}
.guest-notice a:hover{text-decoration:underline}
@media (max-width:640px){
  .nav-progress-pts-label{display:none}
  nav{padding:14px 16px;gap:10px;overflow-x:auto;scrollbar-width:none;-ms-overflow-style:none}
  nav::-webkit-scrollbar{display:none}
  .brand{font-size:15px;flex-shrink:0}
  .nav-links{gap:14px;font-size:12.5px;flex-shrink:0}
  .nav-right{gap:8px;flex-shrink:0}
  .theme-toggle{width:30px;height:30px;margin-left:0}
  .nav-progress-chip{padding:4px 8px 4px 4px}
  .nav-avatar{width:22px;height:22px;font-size:10px}
  .nav-signin-link{padding:7px 12px;font-size:12.5px}
}

main{max-width:980px;margin:0 auto;padding:56px 24px 80px}

/* ---------- Hero ---------- */
.hero{display:flex;align-items:center;gap:40px;margin-bottom:36px}
.hero-text{flex:1;min-width:0}
h1{font-size:40px;font-weight:600;letter-spacing:-0.02em;margin:0 0 14px;line-height:1.15}
.sub{color:var(--muted);font-size:16.5px;margin:0 0 32px;max-width:56ch}
.hero-preview{
  flex-shrink:0;width:220px;height:170px;background:var(--surface);
  border:1px solid var(--border);border-radius:16px;box-shadow:var(--shadow-md);
  overflow:hidden;position:relative;
}
.hero-preview canvas{width:100%;height:100%;display:block}
.hero-preview .hp-label{
  position:absolute;bottom:6px;left:0;right:0;text-align:center;
  font-size:10px;letter-spacing:.08em;text-transform:uppercase;color:var(--muted);
  font-family:'Plus Jakarta Sans',sans-serif;
}

/* ---------- Cards / inputs ---------- */
.card{background:var(--surface);border:1px solid var(--border);border-radius:22px;padding:26px;box-shadow:var(--shadow-sm)}
textarea{
  width:100%;background:var(--surface-alt);color:var(--text);
  border:1px solid var(--border-strong);border-radius:14px;padding:14px;
  font-size:15px;font-family:'Plus Jakarta Sans',sans-serif;resize:vertical;min-height:90px;
  transition:border-color .18s, box-shadow .18s;
}
textarea:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-soft)}
.btn{
  background:var(--gradient);
  color:#fff;border:none;padding:13px 26px;border-radius:14px;
  font-size:15px;font-weight:700;cursor:pointer;margin-top:16px;
  box-shadow:0 8px 20px rgba(124,58,237,0.32);
  transition:transform .18s var(--ease-out-back), box-shadow .18s;
  background-size:160% 160%;
}
.btn:hover{transform:translateY(-2px) scale(1.01);box-shadow:0 12px 26px rgba(124,58,237,0.4);background-position:100% 0}
.btn:active{transform:translateY(0)}
.btn-ghost{
  background:var(--surface);border:1px solid var(--border-strong);color:var(--text);
  padding:9px 17px;border-radius:12px;font-size:13px;cursor:pointer;font-weight:600;
  transition:border-color .18s, background .18s, transform .12s;
}
.btn-ghost:hover{border-color:var(--accent);background:var(--accent-soft);color:var(--accent-dark)}
.btn-ghost:active{transform:scale(.97)}
.chips{display:flex;flex-wrap:wrap;gap:8px;margin-top:16px}
.chip{
  font-size:13px;color:var(--muted);border:1px solid var(--border-strong);
  background:var(--surface);padding:7px 15px;border-radius:24px;cursor:pointer;
  transition:all .18s var(--ease-out);
}
.chip:hover{color:#fff;border-color:transparent;background:var(--gradient);transform:translateY(-1px)}

/* ---------- Sim grid ---------- */
.grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(210px,1fr));gap:18px;margin-top:18px}
.sim-card{
  background:var(--surface);border:1px solid var(--border);border-radius:20px;padding:22px;
  box-shadow:var(--shadow-sm);
  transition:transform .22s var(--ease-out-back), box-shadow .22s, border-color .22s;
  opacity:0;transform:translateY(14px);
  animation:cardIn .5s var(--ease-out-back) forwards;
}
.sim-card:hover{border-color:var(--accent);box-shadow:var(--shadow-md);transform:translateY(-4px) scale(1.01)}
.sim-card .tag{font-size:11px;text-transform:uppercase;letter-spacing:.07em;background:var(--gradient);-webkit-background-clip:text;background-clip:text;color:transparent;margin-bottom:10px;display:block;font-weight:700}
.sim-card h3{margin:0 0 6px;font-size:18px;font-weight:600}
.sim-card p{margin:0;color:var(--muted);font-size:13.5px}
.section-title{font-size:12.5px;text-transform:uppercase;letter-spacing:.09em;color:var(--muted);margin:44px 0 10px;font-weight:600}

@keyframes cardIn{to{opacity:1;transform:translateY(0)}}

/* ---------- Steps (solve page) ---------- */
.step{
  border-left:2px solid var(--border-strong);padding:6px 0 6px 18px;margin-bottom:18px;
  opacity:0;transform:translateX(-10px) scale(.98);
  animation:stepIn .5s var(--ease-out-back) forwards;
  animation-delay:calc(var(--i,0) * 110ms);
}
@keyframes stepIn{to{opacity:1;transform:translateX(0) scale(1)}}
.step .num{font-size:11.5px;color:var(--accent);font-weight:700;letter-spacing:.03em;text-transform:uppercase}
.step h4{margin:3px 0 6px;font-size:16px;font-weight:600;font-family:'Space Grotesk',sans-serif}
.step p{margin:0 0 4px;color:var(--muted);font-size:14px}
.step .formula{margin:10px 0;padding:10px 14px;background:var(--surface-alt);border:1px solid var(--border);border-radius:8px;overflow-x:auto}
.step .result{
  margin-top:8px;padding:8px 14px;background:var(--accent-soft);border-radius:8px;
  display:inline-block;color:var(--accent-dark);font-weight:600;
}
.step .result .katex{color:var(--accent-dark)}

.frame-wrap{border:1px solid var(--border);border-radius:20px;overflow:hidden;margin-top:28px;box-shadow:var(--shadow-sm);background:var(--surface)}
iframe{width:100%;height:560px;border:none;display:block;background:var(--surface)}

/* ---------- Sim controls ---------- */
.sim-header{margin-bottom:14px}
.sim-header h2{margin:0 0 4px;font-size:22px}
.sim-header p{margin:0;color:var(--muted);font-size:13.5px}
.controls{display:flex;align-items:center;gap:12px;margin-bottom:12px;flex-wrap:wrap}
.controls label{font-size:13px;color:var(--muted);min-width:100px;font-weight:500}
.controls input[type=range]{flex:1;accent-color:var(--accent);height:4px}
.controls .val{font-size:13px;min-width:56px;text-align:right;color:var(--text);font-weight:600}
.readout{display:flex;gap:22px;margin-top:12px;font-size:12.5px;color:var(--muted);flex-wrap:wrap}
.readout span{color:var(--text);font-weight:600}
.btn-row{display:flex;gap:8px;margin-bottom:12px}
canvas{width:100%;display:block;border-radius:18px;background:var(--surface);border:1px solid var(--border);box-shadow:var(--shadow-sm)}
.formula-strip{display:flex;flex-wrap:wrap;gap:10px;margin-top:14px}
.formula-pill{
  background:var(--surface);border:1px solid var(--border);border-radius:10px;
  padding:8px 14px;box-shadow:var(--shadow-sm);
}
.formula-pill .fp-label{font-size:10.5px;text-transform:uppercase;letter-spacing:.06em;color:var(--muted);display:block;margin-bottom:3px;font-weight:600}

body.sim-body{padding:20px;max-width:1000px;margin:0 auto}

/* ---------- Tutor chat panel ---------- */
.tutor-panel{
  margin-top:28px;background:var(--surface);border:1px solid var(--border);
  border-radius:20px;box-shadow:var(--shadow-sm);overflow:hidden;
}
.tutor-header{
  padding:16px 22px;border-bottom:1px solid var(--border);
  display:flex;align-items:center;gap:10px;background:var(--surface-alt);
}
.tutor-header .tutor-dot{width:9px;height:9px;border-radius:50%;background:var(--green);box-shadow:0 0 0 3px rgba(21,138,94,.18)}
.tutor-header h3{margin:0;font-size:16px}
.tutor-header p{margin:0;font-size:12.5px;color:var(--muted)}
.tutor-messages{max-height:340px;overflow-y:auto;padding:18px 22px;display:flex;flex-direction:column;gap:12px}
.tutor-msg{
  max-width:82%;padding:10px 14px;border-radius:12px;font-size:14px;line-height:1.55;
  opacity:0;animation:msgIn .35s var(--ease-out) forwards;
}
@keyframes msgIn{from{opacity:0;transform:translateY(6px)}to{opacity:1;transform:translateY(0)}}
.tutor-msg.bot{
  background:var(--surface-alt);border:1px solid var(--border);align-self:flex-start;border-bottom-left-radius:3px;
  display:flex;flex-direction:column;gap:2px;
}
.tutor-msg.user{background:linear-gradient(135deg,var(--accent),var(--accent-dark));color:#fff;align-self:flex-end;border-bottom-right-radius:3px}
.tutor-msg .katex{font-size:1em}
.msg-copy-btn{
  align-self:flex-end;border:none;background:transparent;color:var(--muted);cursor:pointer;
  font-size:11.5px;padding:2px 6px;border-radius:5px;opacity:0;transition:opacity .15s,background .15s,color .15s;
  margin-top:2px;display:inline-flex;align-items:center;justify-content:center;
}
.tutor-msg.bot:hover .msg-copy-btn{opacity:1}
.msg-copy-btn:hover{background:var(--accent-soft);color:var(--accent-dark)}

/* ---------- Generic copy button (answer line, etc.) ---------- */
.copy-btn{
  border:1px solid var(--border-strong);background:var(--surface);color:var(--muted);cursor:pointer;
  font-size:12px;padding:5px 11px;border-radius:8px;font-weight:600;white-space:nowrap;flex-shrink:0;
  transition:all .15s;font-family:'Plus Jakarta Sans',sans-serif;
  display:inline-flex;align-items:center;gap:5px;
}
.copy-btn:hover{border-color:var(--accent);color:var(--accent-dark);background:var(--accent-soft)}
.tutor-chips{display:flex;flex-wrap:wrap;gap:8px;padding:0 22px 16px}
.tutor-chip{
  font-size:12.5px;color:var(--accent-dark);background:var(--accent-soft);
  border:1px solid var(--border-strong);padding:6px 12px;border-radius:16px;cursor:pointer;
  transition:all .18s var(--ease-out);
}
.tutor-chip:hover{background:var(--accent);color:#fff;border-color:var(--accent);transform:translateY(-1px)}
.tutor-input-row{display:flex;gap:8px;padding:14px 18px;border-top:1px solid var(--border);background:var(--surface-alt)}
.tutor-input{
  flex:1;border:1px solid var(--border-strong);border-radius:9px;padding:10px 14px;
  font-family:'Plus Jakarta Sans',sans-serif;font-size:14px;background:var(--surface);color:var(--text);
}
.tutor-input:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-soft)}
.tutor-send{
  background:var(--accent);color:#fff;border:none;border-radius:9px;padding:0 18px;
  font-weight:600;font-size:14px;cursor:pointer;transition:background .18s;
}
.tutor-send:hover{background:var(--accent-dark)}
.typing-dots{display:inline-flex;gap:3px;align-items:center}
.typing-dots span{width:5px;height:5px;border-radius:50%;background:var(--muted);animation:typingBounce 1s infinite}
.typing-dots span:nth-child(2){animation-delay:.15s}
.typing-dots span:nth-child(3){animation-delay:.3s}
@keyframes typingBounce{0%,60%,100%{transform:translateY(0);opacity:.5}30%{transform:translateY(-4px);opacity:1}}

::-webkit-scrollbar{width:9px;height:9px}
::-webkit-scrollbar-thumb{background:var(--border-strong);border-radius:6px}
::-webkit-scrollbar-track{background:transparent}

/* ---------- Floating "tucked away" AI tutor — shared across every page ---------- */
.tutor-fab{
  position:fixed;bottom:24px;right:24px;z-index:50;
  display:flex;align-items:center;gap:8px;
  background:linear-gradient(135deg,var(--accent),var(--accent-dark));color:#fff;border:none;
  padding:13px 20px;border-radius:999px;font-weight:600;font-size:14px;cursor:pointer;
  box-shadow:0 10px 26px rgba(31,111,214,0.34);
  transition:transform .18s var(--ease-out-back), box-shadow .18s;
  font-family:'Plus Jakarta Sans',sans-serif;
}
.tutor-fab:hover{transform:translateY(-2px);box-shadow:0 14px 30px rgba(31,111,214,0.42)}
.tutor-fab .fab-dot{width:8px;height:8px;border-radius:50%;background:#7dffc0;box-shadow:0 0 0 3px rgba(125,255,192,.3)}
.tutor-float-panel{
  position:fixed;bottom:88px;right:24px;z-index:50;width:360px;max-width:calc(100vw - 32px);
  background:var(--surface);border:1px solid var(--border);border-radius:16px;box-shadow:var(--shadow-lg);
  overflow:hidden;display:flex;flex-direction:column;max-height:min(560px,70vh);
  opacity:0;transform:translateY(12px) scale(.98);pointer-events:none;
  transition:opacity .2s var(--ease-out), transform .2s var(--ease-out-back);
}
.tutor-float-panel.open{opacity:1;transform:translateY(0) scale(1);pointer-events:auto}
.tutor-float-header{
  padding:14px 16px;border-bottom:1px solid var(--border);background:var(--surface-alt);
  display:flex;align-items:center;justify-content:space-between;flex-shrink:0;
}
.tutor-float-header h3{margin:0;font-size:14.5px}
.tutor-float-close{background:none;border:none;color:var(--muted);cursor:pointer;padding:2px 6px;display:flex;align-items:center;justify-content:center}
.tutor-float-close:hover{color:var(--text)}
.tutor-float-panel .tutor-messages{max-height:none;flex:1}

/* ---------- Desmos: FAB + floating draggable/resizable panel ---------- */
.desmos-fab{
  position:fixed;bottom:82px;right:24px;z-index:49;width:46px;height:46px;border-radius:50%;
  display:flex;align-items:center;justify-content:center;
  background:var(--surface);color:var(--accent-dark);border:1.5px solid var(--border-strong);
  box-shadow:var(--shadow-md);cursor:pointer;transition:all .18s var(--ease-out-back);
}
.desmos-fab:hover{transform:translateY(-2px);border-color:var(--accent);background:var(--accent-soft)}
.desmos-float-panel{
  position:fixed;bottom:140px;right:24px;z-index:49;width:520px;height:480px;
  min-width:320px;min-height:260px;max-width:calc(100vw - 32px);max-height:calc(100vh - 32px);
  background:var(--surface);border:1px solid var(--border);border-radius:16px;box-shadow:var(--shadow-lg);
  overflow:hidden;display:flex;flex-direction:column;
  opacity:0;transform:translateY(12px) scale(.98);pointer-events:none;
  transition:opacity .2s var(--ease-out), transform .2s var(--ease-out-back);
}
.desmos-float-panel.open{opacity:1;transform:translateY(0) scale(1);pointer-events:auto}
.desmos-float-panel.dragging, .desmos-float-panel.resizing{transition:none}
.desmos-float-header{
  padding:12px 14px;border-bottom:1px solid var(--border);background:var(--surface-alt);
  display:flex;align-items:center;justify-content:space-between;flex-shrink:0;cursor:move;touch-action:none;
}
.desmos-float-header h3{margin:0;font-size:14px}
.desmos-float-actions{display:flex;align-items:center;gap:2px}
.desmos-float-expand,.desmos-float-close{
  background:none;border:none;color:var(--muted);cursor:pointer;padding:5px;display:flex;
  align-items:center;justify-content:center;border-radius:6px;text-decoration:none;
}
.desmos-float-expand:hover,.desmos-float-close:hover{color:var(--text);background:var(--surface)}
.desmos-float-body{flex:1;min-height:0;position:relative}
.desmos-float-body>div{width:100%;height:100%}
.desmos-resize-handle{
  position:absolute;bottom:2px;right:2px;width:16px;height:16px;cursor:nwse-resize;z-index:2;
  background:linear-gradient(135deg,transparent 50%,var(--border-strong) 50%);border-radius:0 0 8px 0;
}

/* ---------- Engine: control rows with paired number input ---------- */
.control-row{display:flex;align-items:center;gap:10px;margin-bottom:11px;flex-wrap:wrap}
.control-row label{font-size:13px;color:var(--muted);min-width:132px;font-weight:500;flex-shrink:0}
.control-row input[type=range]{flex:1;min-width:120px;accent-color:var(--accent);height:4px}
.control-row .num-input{
  width:74px;border:1px solid var(--border-strong);border-radius:7px;padding:5px 8px;
  font-size:13px;text-align:right;background:var(--surface);color:var(--text);
}
.control-row .num-input:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-soft)}
.control-row .unit{font-size:11.5px;color:var(--muted);min-width:32px}

/* ---------- Engine: playback bar ---------- */
.playback-bar{
  display:flex;align-items:center;gap:12px;margin:14px 0;padding:10px 14px;
  background:var(--surface);border:1px solid var(--border);border-radius:12px;box-shadow:var(--shadow-sm);
  flex-wrap:wrap;
}
.pb-play{
  width:38px;height:38px;border-radius:50%;border:none;background:var(--gradient);color:#fff;
  cursor:pointer;display:flex;align-items:center;justify-content:center;flex-shrink:0;font-size:14px;
  transition:transform .15s var(--ease-out-back), box-shadow .15s;
  box-shadow:0 4px 12px rgba(124,58,237,0.32);
}
.pb-play:hover{transform:scale(1.08);box-shadow:0 6px 16px rgba(124,58,237,0.42)}
.pb-scrub{flex:1;min-width:120px;accent-color:var(--accent);height:4px}
.pb-time{font-family:'JetBrains Mono',monospace;font-size:12px;color:var(--muted);min-width:76px;text-align:right}
.pb-speed{
  border:1px solid var(--border-strong);border-radius:7px;background:var(--surface);color:var(--text);
  font-size:12.5px;padding:5px 8px;cursor:pointer;font-family:'Plus Jakarta Sans',sans-serif;
}
.pb-live-toggle{display:flex;align-items:center;gap:6px;font-size:12px;color:var(--muted);cursor:pointer;user-select:none}
.pb-live-toggle input{accent-color:var(--accent)}

/* ---------- Engine: floating live label + canvas wrap ---------- */
.canvas-wrap{position:relative}
.live-label{
  position:absolute;pointer-events:none;transform:translate(-50%,-140%);
  background:rgba(21,34,56,0.92);color:#fff;font-family:'JetBrains Mono',monospace;
  font-size:11px;line-height:1.5;padding:6px 9px;border-radius:8px;white-space:nowrap;
  opacity:0;transition:opacity .15s, left .05s linear, top .05s linear;
  box-shadow:var(--shadow-md);z-index:5;
}
.live-label.on{opacity:1}
.live-label:after{
  content:'';position:absolute;left:50%;bottom:-5px;transform:translateX(-50%);
  border:5px solid transparent;border-top-color:rgba(21,34,56,0.92);
}

/* ---------- Sim runner page ---------- */
body.runner-body{padding:0}
.runner-topbar{
  display:flex;align-items:center;justify-content:space-between;padding:14px 24px;
  background:rgba(255,255,255,0.75);backdrop-filter:blur(10px);border-bottom:1px solid var(--border);
  position:sticky;top:0;z-index:20;
}
.runner-back{
  display:flex;align-items:center;gap:6px;font-size:13.5px;font-weight:500;color:var(--muted);
  transition:color .18s;
}
.runner-back:hover{color:var(--accent)}
.runner-crumb{font-size:12px;color:var(--muted)}
.runner-crumb b{color:var(--text);font-weight:600}
.runner-main{max-width:900px;margin:0 auto;padding:28px 24px 60px}

/* ---------- Simulations index (by unit) ---------- */
.unit-block{margin-bottom:34px}
.unit-block h3{font-size:17px;margin:0 0 4px}
.unit-block .unit-sub{color:var(--muted);font-size:12.5px;margin:0 0 14px}
.mini-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(190px,1fr));gap:12px}
.mini-card{
  background:var(--surface);border:1px solid var(--border);border-radius:12px;padding:14px 16px;
  box-shadow:var(--shadow-sm);transition:transform .18s var(--ease-out-back),border-color .18s,box-shadow .18s;
  font-size:13.5px;
}
.mini-card:hover{border-color:var(--accent);box-shadow:var(--shadow-md);transform:translateY(-2px)}
.mini-card .mc-title{font-weight:600;display:block;margin-bottom:3px}
.mini-card .mc-badge{
  font-size:9.5px;text-transform:uppercase;letter-spacing:.06em;color:var(--accent-dark);
  background:var(--accent-soft);padding:2px 7px;border-radius:6px;display:inline-block;margin-top:6px;
}
.filter-row{display:flex;flex-wrap:wrap;gap:8px;margin:16px 0 8px}
.filter-chip{
  font-size:12.5px;padding:6px 13px;border-radius:16px;border:1px solid var(--border-strong);
  background:var(--surface);color:var(--muted);cursor:pointer;transition:all .18s var(--ease-out);
}
.filter-chip.active,.filter-chip:hover{background:var(--accent);color:#fff;border-color:var(--accent)}

/* ---------- Sidebar (chat history) ---------- */
.app-shell{display:flex;min-height:100vh}
.sidebar{
  width:250px;flex-shrink:0;background:var(--surface);border-right:1px solid var(--border);
  transition:width .24s var(--ease-out), padding .24s var(--ease-out);
  overflow:hidden;display:flex;flex-direction:column;
}
.sidebar.collapsed{width:56px}
.sidebar-top{display:flex;align-items:center;justify-content:space-between;padding:16px 14px;border-bottom:1px solid var(--border);flex-shrink:0}
.sidebar-toggle{
  width:28px;height:28px;border-radius:8px;border:1px solid var(--border-strong);background:var(--surface);
  color:var(--muted);cursor:pointer;display:flex;align-items:center;justify-content:center;flex-shrink:0;
  transition:all .18s;
}
.sidebar-toggle:hover{border-color:var(--accent);color:var(--accent)}
.sidebar-label{font-size:12px;text-transform:uppercase;letter-spacing:.07em;color:var(--muted);font-weight:600;white-space:nowrap}
.sidebar.collapsed .sidebar-label,.sidebar.collapsed .sidebar-entry-text{display:none}
.sidebar-list{overflow-y:auto;flex:1;padding:8px}
.sidebar-entry{
  display:flex;align-items:center;gap:9px;padding:9px 10px;border-radius:9px;cursor:pointer;
  font-size:13px;color:var(--text);margin-bottom:2px;transition:background .15s;white-space:nowrap;overflow:hidden;
}
.sidebar-entry:hover{background:var(--accent-soft)}
.sidebar-entry.active{background:var(--accent-soft);font-weight:600}
.sidebar-entry.active .se-dot{background:var(--accent-dark);box-shadow:0 0 0 3px rgba(31,111,214,.18)}
.sidebar-entry .se-dot{width:7px;height:7px;border-radius:50%;background:var(--accent);flex-shrink:0}
.sidebar-entry-text{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;flex:1}
.sidebar-empty{padding:14px 12px;font-size:12.5px;color:var(--muted);line-height:1.5}
.sidebar.collapsed .sidebar-empty{display:none}
.app-content{flex:1;min-width:0}

/* ---------- Sidebar: search, sections, per-entry actions, clear-all ---------- */
.sidebar-search-wrap{padding:2px 12px 10px;flex-shrink:0}
.sidebar.collapsed .sidebar-search-wrap{display:none}
.sidebar-search{
  width:100%;background:var(--surface-alt);border:1px solid var(--border);border-radius:9px;
  padding:7px 10px;font-size:12.5px;color:var(--text);font-family:'Plus Jakarta Sans',sans-serif;
  transition:border-color .18s, box-shadow .18s;
}
.sidebar-search:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-soft)}
.sidebar-search::placeholder{color:var(--muted)}
.sidebar-section-label{
  font-size:10.5px;text-transform:uppercase;letter-spacing:.07em;color:var(--muted);font-weight:700;
  padding:12px 10px 5px;
}
.sidebar.collapsed .sidebar-section-label{display:none}
.sidebar-entry{position:relative;padding-right:6px}
.sidebar-entry.pinned .se-dot{background:var(--warm)}
.se-actions{display:flex;align-items:center;gap:2px;opacity:0;transition:opacity .15s;flex-shrink:0}
.sidebar-entry:hover .se-actions{opacity:1}
.sidebar-entry.pinned .se-pin{opacity:1}
.sidebar.collapsed .se-actions{display:none}
.se-btn{
  width:22px;height:22px;border:none;background:transparent;border-radius:6px;cursor:pointer;
  font-size:11.5px;display:flex;align-items:center;justify-content:center;color:var(--muted);
  transition:background .15s, color .15s;flex-shrink:0;line-height:1;
}
.se-btn:hover{background:var(--surface);color:var(--accent-dark)}
.se-delete:hover{color:var(--pos)}
.sidebar-bottom{padding:10px 12px;border-top:1px solid var(--border);flex-shrink:0}
.sidebar.collapsed .sidebar-bottom{display:none}
.sidebar-clear{
  width:100%;background:transparent;border:1px solid var(--border-strong);color:var(--muted);
  padding:8px 10px;border-radius:9px;font-size:12px;font-weight:600;cursor:pointer;
  transition:all .18s;font-family:'Plus Jakarta Sans',sans-serif;
  display:flex;align-items:center;justify-content:center;gap:6px;
}
.sidebar-clear:hover{border-color:var(--pos);color:var(--pos);background:rgba(225,29,103,0.06)}

/* ---------- Image upload stub ---------- */
.upload-row{display:flex;align-items:center;gap:10px;margin-top:12px}
.upload-btn{
  display:flex;align-items:center;gap:7px;border:1px dashed var(--border-strong);background:var(--surface-alt);
  color:var(--muted);padding:8px 14px;border-radius:9px;font-size:13px;cursor:pointer;transition:all .18s;
}
.upload-btn:hover{border-color:var(--accent);color:var(--accent-dark);background:var(--accent-soft)}
.upload-thumb{
  display:flex;align-items:center;gap:8px;background:var(--accent-soft);border:1px solid var(--border-strong);
  border-radius:9px;padding:5px 10px 5px 5px;font-size:12.5px;color:var(--accent-dark);
}
.upload-thumb img{width:30px;height:30px;object-fit:cover;border-radius:6px}
.upload-thumb .ut-remove{cursor:pointer;color:var(--muted);font-weight:700;padding:0 3px}
.upload-thumb .ut-remove:hover{color:var(--pos)}

@media (max-width:640px){
  .hero{flex-direction:column;align-items:stretch}
  .hero-preview{width:100%;height:150px}
  .sidebar{position:fixed;left:0;top:0;bottom:0;z-index:30;box-shadow:var(--shadow-lg)}
  .sidebar.collapsed{width:0;border:none}
}

.theme-switching, .theme-switching *{transition:none !important}

/* ---------- Minimal line-icon slots (replacing emoji) ---------- */
.icon-slot{display:inline-flex;align-items:center;justify-content:center;flex-shrink:0}
.icon-slot svg{display:block}

/* ---------- Theme toggle button ---------- */
.theme-toggle{
  width:34px;height:34px;border-radius:10px;border:1px solid var(--border-strong);background:var(--surface);
  color:var(--text);cursor:pointer;font-size:15px;display:flex;align-items:center;justify-content:center;
  transition:all .18s;margin-left:18px;flex-shrink:0;
}
.theme-toggle:hover{border-color:var(--accent);background:var(--accent-soft);transform:translateY(-1px)}
nav{gap:14px}
nav .nav-links{margin-right:auto}

/* ---------- Dark theme ---------- */
:root[data-theme="dark"]{
  --bg:#131022;
  --bg-grad:#1c1636;
  --surface:#1b1730;
  --surface-alt:#221d3c;
  --border:#332c54;
  --border-strong:#453a6e;
  --text:#ede9fe;
  --muted:#a49bc9;
  --accent:#a78bfa;
  --accent-dark:#c4b5fd;
  --accent-soft:rgba(167,139,250,0.16);
  --grad-a:#6366f1;
  --grad-b:#c084fc;
  --grad-c:#f472b6;
  --warm:#f0a865;
  --warm-soft:rgba(224,138,62,0.18);
  --pos:#fb7185;
  --neg:#818cf8;
  --green:#2dd4bf;
  --success:#6ee7b7;
  --success-soft:rgba(16,185,129,0.14);
  --success-border:rgba(16,185,129,0.35);
  --error:#fca5a5;
  --error-soft:rgba(239,68,68,0.14);
  --error-border:rgba(239,68,68,0.35);
  --shadow-sm:0 2px 10px rgba(0,0,0,0.28);
  --shadow-md:0 12px 30px rgba(0,0,0,0.36);
  --shadow-lg:0 20px 48px rgba(0,0,0,0.44);
}
:root[data-theme="dark"] body{
  background:
    radial-gradient(1100px 500px at 12% -10%, var(--bg-grad), transparent),
    radial-gradient(900px 500px at 105% 5%, #2a1a34, transparent),
    var(--bg);
}
:root[data-theme="dark"] nav{background:rgba(19,16,34,0.75)}
:root[data-theme="dark"] .runner-topbar{background:rgba(19,16,34,0.8)}
:root[data-theme="dark"] .theme-toggle{color:#f0d78c}