/* MechForge Toolkit — standalone design system
   Fully self-contained; imported by every toolkit_*.html page.
   Matches the MechForge Reference Hub visual language exactly.          */

/* ─── Design tokens ─────────────────────────────────────────────────── */
:root{
  --ink:#0f0e0d; --paper:#f7f4ef; --cream:#ede8df; --accent:#c0392b;
  --gold:#b8860b; --steel:#2c3e50; --muted:#6b6560; --rule:#d4cec5;
  --highlight:#fff3cd; --card:#ffffff;
  --header-h:64px; --sidebar-w:280px;
  --ok:#1e8449;
  --shadow:0 1px 2px rgba(0,0,0,.04), 0 12px 30px -20px rgba(40,30,20,.45);
}
html[data-theme="dark"]{
  --ink:#ece7df; --paper:#16161a; --cream:#20212a; --accent:#e06a5b;
  --gold:#d4a431; --steel:#9fb4c9; --muted:#9a948c; --rule:#33343f;
  --highlight:#3a3520; --card:#1d1e26;
  --shadow:0 1px 2px rgba(0,0,0,.3), 0 14px 34px -20px rgba(0,0,0,.7);
}
*{box-sizing:border-box; margin:0; padding:0}
html{scroll-behavior:smooth}
body{
  background:var(--paper); color:var(--ink);
  font-family:"Source Serif 4",Georgia,serif; font-weight:400;
  font-size:17px; line-height:1.65; -webkit-font-smoothing:antialiased;
  transition:background .25s ease, color .25s ease;
}
h1,h2,h3,h4{font-family:"Playfair Display",Georgia,serif; line-height:1.15; margin:0}
a{color:var(--accent); text-decoration:none}
p{margin-bottom:14px}
.mono{font-family:"IBM Plex Mono",monospace}

/* ─── Top bar ────────────────────────────────────────────────────────── */
.topbar{
  position:fixed; top:0; left:0; right:0; height:var(--header-h); z-index:60;
  display:flex; align-items:center; gap:18px; padding:0 22px;
  background:var(--steel); color:#f4f1ea; border-bottom:1px solid rgba(0,0,0,.2);
}
html[data-theme="dark"] .topbar{background:#101218}
.logo{
  font-family:"Playfair Display",serif; font-weight:900; font-size:23px;
  letter-spacing:.3px; white-space:nowrap; color:#f4f1ea; text-decoration:none;
}
.logo b{color:var(--accent); font-weight:900}
.topbar .label{
  font-family:"IBM Plex Mono",monospace; font-size:12px; letter-spacing:.18em;
  text-transform:uppercase; color:#cdd6df; white-space:nowrap;
}
.topbar .label .sep{opacity:.45; margin:0 8px}
.topbar-spacer{flex:1}
.iconbtn{
  background:rgba(255,255,255,.08); color:#f4f1ea; border:1px solid rgba(255,255,255,.18);
  border-radius:8px; width:36px; height:36px; cursor:pointer; font-size:16px;
  display:grid; place-items:center; font-family:inherit;
}
.iconbtn:hover{background:rgba(255,255,255,.18)}
.hamburger{display:none}
/* scroll progress strip */
.progress{position:fixed; top:var(--header-h); left:0; height:3px; background:var(--accent); width:0; z-index:59; transition:width .08s linear}

/* ─── Sidebar ────────────────────────────────────────────────────────── */
.sidebar{
  position:fixed; top:var(--header-h); bottom:0; left:0; width:var(--sidebar-w); z-index:40;
  background:var(--cream); border-right:1px solid var(--rule); overflow-y:auto; padding:14px 0 60px;
}
.sidebar .grp{
  font-family:"IBM Plex Mono",monospace; font-size:10px; letter-spacing:.2em; text-transform:uppercase;
  color:var(--muted); padding:14px 24px 5px;
}
.sidebar a{
  display:flex; align-items:center; gap:10px; padding:7px 24px; color:var(--ink);
  font-size:14.5px; border-left:3px solid transparent;
}
.sidebar a:hover{background:rgba(192,57,43,.07)}
.sidebar a.active{border-left-color:var(--accent); color:var(--accent); background:rgba(192,57,43,.08); font-weight:600}
.sidebar a .ti{width:20px; text-align:center; opacity:.7; flex:none}
.sidebar .rule{border:0; border-top:1px solid var(--rule); margin:10px 20px}
.sidebar .back-link{color:var(--muted); font-size:13.5px}
.sidebar .back-link:hover{color:var(--accent)}

/* ─── Main ───────────────────────────────────────────────────────────── */
main.content{
  margin-left:var(--sidebar-w); margin-top:var(--header-h);
  max-width:960px; padding:44px 60px 100px;
}
h1{font-family:"Playfair Display",serif; font-weight:900; font-size:clamp(28px,4vw,42px); margin-bottom:8px}
.subtitle{color:var(--muted); font-style:italic; margin-bottom:28px; max-width:68ch}
h2{
  font-family:"Playfair Display",serif; font-weight:700; font-size:1.45rem;
  margin:44px 0 14px; padding-bottom:8px; border-bottom:2px solid var(--rule);
}
h3{font-family:"Playfair Display",serif; font-size:1.2rem; margin:24px 0 10px}

/* ─── Component blocks ───────────────────────────────────────────────── */
.concept-block{
  background:var(--cream); border-left:4px solid var(--steel);
  padding:16px 20px; border-radius:0 8px 8px 0; margin:18px 0;
}
.concept-block h4{font-size:18px; margin-bottom:6px}
.formula-box{
  background:var(--card); border:1.5px solid var(--gold);
  padding:16px 22px; margin:20px 0; border-radius:10px; position:relative;
  box-shadow:var(--shadow); overflow:hidden;
}
.formula-box::before{
  content:"FORMULA"; position:absolute; top:-9px; left:14px;
  background:var(--paper); color:var(--gold);
  font-family:"IBM Plex Mono",monospace; font-size:.66rem; letter-spacing:.16em; padding:0 8px;
}
html[data-theme="dark"] .formula-box::before{background:var(--cream)}
.formula-title{font-family:"IBM Plex Mono",monospace; font-size:.78rem; letter-spacing:.08em; color:var(--muted); margin-bottom:8px}
.key-idea{
  background:var(--highlight); border:1px solid var(--gold);
  border-radius:8px; padding:14px 18px; margin:18px 0; font-size:.95rem;
}
.theorem-box{
  background:var(--card); border:1px solid var(--steel); border-left:5px solid var(--steel);
  border-radius:8px; padding:14px 18px; margin:18px 0;
}
.theorem-box .tlabel{
  font-family:"IBM Plex Mono",monospace; font-size:11px; letter-spacing:.16em;
  text-transform:uppercase; color:var(--steel); margin-bottom:6px;
}
.admin-note{
  background:var(--card); border:1.5px dashed var(--accent);
  padding:14px 18px; margin:18px 0; border-radius:8px; font-size:.94rem;
}
.admin-note::before{
  content:"ADMIN NOTE"; display:block; color:var(--accent);
  font-family:"IBM Plex Mono",monospace; font-size:.66rem; letter-spacing:.16em; margin-bottom:6px;
}
.note-sm{font-size:13px; color:var(--muted); font-style:italic; margin-top:8px}

/* ─── Calculator panel ───────────────────────────────────────────────── */
.calc{
  background:var(--card); border:1px solid var(--rule); border-radius:12px;
  box-shadow:var(--shadow); padding:24px 26px; margin:20px 0;
}
.calc-title{font-family:"Playfair Display",serif; font-weight:700; font-size:1.2rem; margin-bottom:4px}
.calc-sub{font-size:.9rem; color:var(--muted); margin-bottom:18px; font-style:italic}

.calc-grid{display:grid; grid-template-columns:repeat(auto-fit,minmax(160px,1fr)); gap:14px; margin:12px 0}
.field{margin:0}
.field label{
  display:block; font-family:"IBM Plex Mono",monospace; font-size:.72rem;
  letter-spacing:.1em; color:var(--muted); text-transform:uppercase; margin-bottom:5px;
}
.field input,.field select,.field textarea{
  width:100%; font-family:"IBM Plex Mono",monospace; font-size:.95rem;
  padding:9px 11px; border:1px solid var(--rule); border-radius:8px;
  background:var(--paper); color:var(--ink); outline:none;
}
.field input:focus,.field select:focus,.field textarea:focus{
  border-color:var(--gold); background:var(--card); outline:2px solid rgba(184,134,11,.3);
}
.field textarea{min-height:90px; resize:vertical}
.field .hint{font-size:.78rem; color:var(--muted); margin-top:4px; font-family:"Source Serif 4",serif; text-transform:none; letter-spacing:0}
.field .unit{color:var(--accent); margin-left:4px}

.btn-row{display:flex; gap:8px; flex-wrap:wrap; margin-top:16px}
button.btn{
  font-family:"IBM Plex Mono",monospace; font-size:.8rem; letter-spacing:.05em;
  padding:9px 18px; border:0; border-radius:8px; cursor:pointer;
  background:var(--steel); color:#fff; transition:filter .12s;
}
button.btn:hover{filter:brightness(1.1)}
button.btn.primary{background:var(--accent)}
button.btn.ghost{background:transparent; color:var(--steel); border:1px solid var(--rule)}
button.btn.ghost:hover{border-color:var(--steel)}
button.btn.small{padding:5px 10px; font-size:.72rem}
/* hub class aliases */
.btn{
  font-family:"IBM Plex Mono",monospace; font-size:12px; letter-spacing:.05em;
  border:0; border-radius:8px; padding:10px 16px; cursor:pointer;
  background:var(--steel); color:#fff; transition:filter .12s;
}
.btn:hover{filter:brightness(1.08)}
.btn.accent,.btn.primary{background:var(--accent)}
.btn.ghost{background:transparent; color:var(--steel); border:1px solid var(--rule)}
.btn.small{padding:5px 10px; font-size:11px}

/* ─── Result frame ───────────────────────────────────────────────────── */
.result{
  background:var(--card); border:1.5px solid var(--gold);
  padding:18px 22px; margin-top:18px; border-radius:10px; position:relative;
  display:none; box-shadow:var(--shadow);
}
.result.show{display:block}
.result::before{
  content:"RESULT"; position:absolute; top:-9px; left:14px;
  background:var(--card); color:var(--gold);
  font-family:"IBM Plex Mono",monospace; font-size:.66rem; letter-spacing:.16em; padding:0 8px;
}
.result .big{font-size:1.15rem; margin:6px 0; font-family:"IBM Plex Mono",monospace; font-weight:600}
.result table{border-collapse:collapse; width:100%; margin:8px 0; font-size:.95rem}
.result th,.result td{border:1px solid var(--rule); padding:7px 12px; text-align:left}
.result th{background:var(--cream); font-family:"IBM Plex Mono",monospace; font-size:.72rem; letter-spacing:.08em; text-transform:uppercase; color:var(--muted)}
.result .err{color:var(--accent); font-weight:600}

/* result-panel alias (used by hub-style pages) */
.result-panel{background:var(--cream); border:1px solid var(--rule); border-radius:10px; padding:16px 18px}
.result-panel .rrow{display:flex; justify-content:space-between; gap:16px; padding:7px 0; border-bottom:1px dashed var(--rule); align-items:baseline}
.result-panel .rrow:last-child{border-bottom:0}
.result-panel .rk{color:var(--muted); font-size:14px}
.result-panel .rv{font-family:"IBM Plex Mono",monospace; font-weight:600; font-size:16px}
.result-panel .rv.big{font-size:21px; color:var(--accent)}

/* ─── Step-by-step panel ─────────────────────────────────────────────── */
.steps{
  background:var(--cream); border-left:4px solid var(--gold);
  padding:16px 20px; margin-top:16px; border-radius:0 8px 8px 0; display:none;
}
.steps.show{display:block}
.steps::before{
  content:"STEP BY STEP"; display:block; font-family:"IBM Plex Mono",monospace;
  font-size:.66rem; letter-spacing:.16em; color:var(--gold); margin-bottom:10px;
}
.steps .step{padding:8px 0; border-bottom:1px dashed var(--rule); font-size:.95rem}
.steps .step:last-child{border-bottom:0}
.steps .step .snum{font-family:"IBM Plex Mono",monospace; color:var(--accent); font-size:.75rem; margin-right:8px}

/* ─── SaaS tier gating ───────────────────────────────────────────────── */
body.tier-free .steps.show{position:relative; overflow:hidden}
body.tier-free .steps.show .step{filter:blur(4px); pointer-events:none; user-select:none}
body.tier-free .steps.show::after{
  content:""; position:absolute; inset:0;
  background:linear-gradient(to bottom, rgba(237,232,223,0) 20%, rgba(237,232,223,.95) 60%);
  pointer-events:none;
}
html[data-theme="dark"] body.tier-free .steps.show::after{
  background:linear-gradient(to bottom, rgba(32,33,42,0) 20%, rgba(32,33,42,.95) 60%);
}
body.tier-free .steps.show .upgrade-wall{
  position:absolute; bottom:0; left:0; right:0; padding:20px;
  display:flex; flex-direction:column; align-items:center; gap:10px;
  pointer-events:all;
}
.upgrade-wall{display:none}
body.tier-free .steps.show .upgrade-wall{display:flex}
.upgrade-wall p{font-family:"IBM Plex Mono",monospace; font-size:12px; letter-spacing:.08em; color:var(--muted); text-align:center; margin:0}
.upgrade-wall .up-btn{
  font-family:"IBM Plex Mono",monospace; font-size:12px; letter-spacing:.06em;
  background:var(--accent); color:#fff; border:0; border-radius:8px;
  padding:10px 22px; cursor:pointer; font-weight:600;
}
.upgrade-wall .up-btn:hover{filter:brightness(1.1)}

/* ─── Tabs ───────────────────────────────────────────────────────────── */
.tabs{display:flex; gap:0; border-bottom:2px solid var(--rule); margin:18px 0 0; flex-wrap:wrap}
.tabs button{
  font-family:"IBM Plex Mono",monospace; font-size:.76rem; letter-spacing:.06em;
  padding:9px 15px; border:0; background:transparent; color:var(--muted);
  cursor:pointer; border-bottom:3px solid transparent; margin-bottom:-2px;
}
.tabs button.active,.tabs button.on{color:var(--accent); border-bottom-color:var(--accent); font-weight:600}
.tabpane,.tabpanel{display:none; padding-top:16px}
.tabpane.active,.tabpanel.on,.tabpane.on{display:block}

/* ─── Tables ─────────────────────────────────────────────────────────── */
.tbl-wrap{overflow-x:auto; border:1px solid var(--rule); border-radius:10px}
table.data{width:100%; border-collapse:collapse; font-size:14px}
table.data th,table.data td{padding:9px 12px; text-align:left; border-bottom:1px solid var(--rule); white-space:nowrap}
table.data th{font-family:"IBM Plex Mono",monospace; font-size:11px; letter-spacing:.06em; text-transform:uppercase; color:var(--muted); background:var(--cream); cursor:pointer; position:sticky; top:0}
table.data th:hover{color:var(--accent)}
table.data tbody tr:hover{background:var(--cream)}
table.data td.num{font-family:"IBM Plex Mono",monospace; text-align:right}
table.data tr.sel{background:rgba(184,134,11,.12)}
.filterbar{display:flex; flex-wrap:wrap; gap:10px; align-items:center; margin-bottom:14px}
.filterbar input,.filterbar select{padding:8px 11px; border:1px solid var(--rule); border-radius:8px; background:var(--paper); color:var(--ink); font-family:"IBM Plex Mono",monospace; font-size:13px}
.chip-row{display:flex; flex-wrap:wrap; gap:8px}
.fchip{font-family:"IBM Plex Mono",monospace; font-size:11.5px; padding:5px 12px; border-radius:20px; border:1px solid var(--rule); cursor:pointer; background:var(--paper); color:var(--ink)}
.fchip.on{background:var(--accent); color:#fff; border-color:var(--accent)}

/* ─── Matrix inputs ──────────────────────────────────────────────────── */
.matrix-wrap{
  display:inline-block; border-left:2px solid var(--steel); border-right:2px solid var(--steel);
  padding:6px 10px; margin:8px 12px 8px 0; vertical-align:middle;
}
.matrix-wrap table{border-collapse:separate; border-spacing:5px}
.matrix-wrap input{
  width:58px; text-align:center; font-family:"IBM Plex Mono",monospace; font-size:.9rem;
  padding:6px 4px; border:1px solid var(--rule); background:var(--paper); color:var(--ink); border-radius:6px;
}
.matrix-wrap input:focus{border-color:var(--gold); background:var(--card); outline:none}

/* ─── Badges ─────────────────────────────────────────────────────────── */
.badge{display:inline-block; font-family:"IBM Plex Mono",monospace; font-size:10.5px; letter-spacing:.1em; text-transform:uppercase; padding:2px 8px; border-radius:20px; border:1px solid var(--rule)}
.badge.clear{background:rgba(30,132,73,.12); color:var(--ok); border-color:var(--ok)}
.badge.inter{background:rgba(192,57,43,.12); color:var(--accent); border-color:var(--accent)}
.badge.trans{background:rgba(184,134,11,.14); color:var(--gold); border-color:var(--gold)}

/* ─── Figure / diagram ───────────────────────────────────────────────── */
.fig-container{margin:20px 0; text-align:center}
.fig-container svg{max-width:100%; height:auto; background:var(--card); border:1px solid var(--rule); border-radius:8px}
.fig-caption{font-size:.85rem; color:var(--muted); font-style:italic; margin-top:8px}
.fig-ref{font-family:"IBM Plex Mono",monospace; font-size:.7rem; letter-spacing:.1em; color:var(--gold)}
canvas.plot{width:100%; max-width:680px; border:1px solid var(--rule); border-radius:8px; background:var(--card); display:block; margin:16px auto}
svg .vlabel{font-family:"IBM Plex Mono",monospace; font-size:14px; fill:var(--steel); transition:fill .15s}
svg .vlabel.lit{fill:var(--accent); font-weight:700}
svg .shape-line{stroke:var(--steel); stroke-width:2; fill:none}
svg .shape-fill{fill:var(--cream); stroke:var(--steel); stroke-width:2}
svg .dim{stroke:var(--gold); stroke-width:1.2}
svg .axis{stroke:var(--muted); stroke-width:1}
svg .curve{fill:none; stroke:var(--steel); stroke-width:1.6}
svg .curve.accent{stroke:var(--accent); stroke-width:2}
svg text.axl{fill:var(--muted); font-family:"IBM Plex Mono",monospace; font-size:11px}

/* ─── Chart card ─────────────────────────────────────────────────────── */
.chartcard{background:var(--card); border:1px solid var(--rule); border-radius:12px; box-shadow:var(--shadow); padding:18px 20px; margin:18px 0}
.chartcard h4{margin:0 0 2px}
.chart-host{width:100%; overflow-x:auto}

/* ─── Misc helpers ───────────────────────────────────────────────────── */
.varchips{display:flex; flex-wrap:wrap; gap:7px; margin-top:10px}
.varchip{font-family:"IBM Plex Mono",monospace; font-size:12px; border:1px solid var(--rule); background:var(--paper); border-radius:20px; padding:4px 11px; cursor:pointer; transition:all .12s}
.varchip:hover{border-color:var(--steel)}
.varchip.active{background:var(--steel); color:#fff; border-color:var(--steel)}
.vardetail{margin-top:10px; padding:10px 14px; border-left:3px solid var(--gold); background:var(--highlight); border-radius:0 8px 8px 0; font-size:14.5px; display:none}
.vardetail.show{display:block}
.vardetail .vu{font-family:"IBM Plex Mono",monospace; color:var(--accent)}
.collapse{margin-top:10px}
.collapse summary{cursor:pointer; font-family:"IBM Plex Mono",monospace; font-size:12px; letter-spacing:.05em; color:var(--steel); list-style:none}
.collapse summary::-webkit-details-marker{display:none}
.collapse summary::before{content:"▸ "; color:var(--accent)}
.collapse[open] summary::before{content:"▾ "}
.collapse .cbody{padding:10px 4px 4px; color:var(--muted); font-size:15px}
.stackrow{display:grid; grid-template-columns:1.4fr 1fr 1fr auto; gap:8px; margin-bottom:8px; align-items:center}
.stackrow input{padding:8px 10px; border:1px solid var(--rule); border-radius:7px; background:var(--paper); color:var(--ink); font-family:"IBM Plex Mono",monospace; font-size:13px; width:100%}
.stackrow .del{background:none; border:0; color:var(--accent); cursor:pointer; font-size:18px}
.kfacts{display:flex; flex-wrap:wrap; gap:8px; margin:8px 0 4px}
.kfact{font-family:"IBM Plex Mono",monospace; font-size:11px; background:var(--cream); border:1px solid var(--rule); border-radius:6px; padding:4px 9px}
.toast{
  position:fixed; bottom:26px; left:50%; transform:translateX(-50%) translateY(20px);
  background:var(--steel); color:#fff; padding:11px 20px; border-radius:10px;
  font-family:"IBM Plex Mono",monospace; font-size:13px; opacity:0; transition:all .25s;
  z-index:90; pointer-events:none;
}
.toast.show{opacity:1; transform:translateX(-50%) translateY(0)}
#scratchOut{min-height:44px}
.gdt-sym{font-size:20px; text-align:center}
.inline-2{display:grid; grid-template-columns:1fr auto; gap:8px; align-items:end}
.ashby-wrap{position:relative}
#ashbyTip{position:absolute; pointer-events:none; background:var(--steel); color:#fff; font-family:"IBM Plex Mono",monospace; font-size:11px; padding:5px 8px; border-radius:6px; display:none; white-space:nowrap; z-index:5}

/* ─── Hub grid (toolkit_hub.html) ────────────────────────────────────── */
.hub-grid{display:grid; grid-template-columns:repeat(auto-fill,minmax(240px,1fr)); gap:18px; margin:18px 0 32px}
.hub-card{
  background:var(--card); border:1px solid var(--rule); border-top:3px solid var(--gold);
  border-radius:0 0 10px 10px; padding:20px; text-decoration:none; color:var(--ink);
  display:block; transition:box-shadow .15s, transform .15s;
  box-shadow:var(--shadow);
}
.hub-card:hover{box-shadow:0 6px 20px rgba(15,14,13,.14); transform:translateY(-2px)}
.hub-card .hc-tag{font-family:"IBM Plex Mono",monospace; font-size:.64rem; letter-spacing:.14em; color:var(--accent); text-transform:uppercase}
.hub-card h4{font-family:"Playfair Display",serif; font-size:1.1rem; margin:6px 0 8px}
.hub-card p{font-size:.86rem; color:var(--muted); margin:0; line-height:1.5}

/* ─── Upgrade / auth modal ───────────────────────────────────────────── */
.overlay{position:fixed; inset:0; background:rgba(15,14,13,.55); z-index:120; display:none; align-items:center; justify-content:center}
.overlay.open{display:flex}
.modal{width:min(480px,94vw); background:var(--card); border:1px solid var(--rule); border-radius:14px; box-shadow:0 30px 80px -20px rgba(0,0,0,.5); overflow:hidden}
.modal-head{display:flex; align-items:center; justify-content:space-between; padding:18px 22px; border-bottom:1px solid var(--rule)}
.modal-head h3{font-size:21px; margin:0}
.modal-body{padding:22px}
.modal-body .field{margin:0 0 14px}
.modal-foot{display:flex; justify-content:space-between; gap:10px; padding:16px 22px; border-top:1px solid var(--rule); flex-wrap:wrap; align-items:center}
.modal-foot .hint{font-family:"IBM Plex Mono",monospace; font-size:11px; color:var(--muted)}
.seg{display:inline-flex; border:1px solid var(--rule); border-radius:8px; overflow:hidden}
.seg button{background:var(--paper); color:var(--muted); border:0; padding:8px 16px; cursor:pointer; font-family:"IBM Plex Mono",monospace; font-size:12px}
.seg button.on{background:var(--steel); color:#fff}
.pro-banner{
  background:linear-gradient(135deg, var(--steel) 0%, #1a2634 100%);
  color:#f4f1ea; border-radius:10px; padding:20px 24px; margin:18px 0;
  display:flex; align-items:center; justify-content:space-between; gap:16px; flex-wrap:wrap;
}
.pro-banner .pb-text h4{font-size:18px; margin-bottom:4px; color:#fff}
.pro-banner .pb-text p{font-size:13px; color:#cdd6df; margin:0}
.pro-banner .pb-btn{
  font-family:"IBM Plex Mono",monospace; font-size:12px; letter-spacing:.06em;
  background:var(--accent); color:#fff; border:0; border-radius:8px;
  padding:10px 20px; cursor:pointer; white-space:nowrap; font-weight:600;
}
.pro-badge{
  font-family:"IBM Plex Mono",monospace; font-size:10px; letter-spacing:.12em;
  background:linear-gradient(135deg,var(--gold),#e6a817); color:#fff;
  border-radius:4px; padding:2px 7px; text-transform:uppercase; vertical-align:middle; margin-left:6px;
}
.free-tag{
  font-family:"IBM Plex Mono",monospace; font-size:10px; letter-spacing:.1em;
  background:var(--cream); color:var(--muted); border:1px solid var(--rule);
  border-radius:4px; padding:2px 7px; text-transform:uppercase; vertical-align:middle; margin-left:6px;
}
/* tier badge in topbar */
.tier-badge{
  font-family:"IBM Plex Mono",monospace; font-size:10.5px; letter-spacing:.08em;
  border-radius:6px; padding:4px 10px; cursor:pointer; border:0;
}
.tier-badge.free{background:rgba(255,255,255,.1); color:#cdd6df}
.tier-badge.pro{background:var(--gold); color:#fff}

/* ─── Print ──────────────────────────────────────────────────────────── */
@media print{
  .topbar,.sidebar,.progress,.btn,.btn-row{display:none!important}
  main.content{margin:0; max-width:100%; padding:0}
  .calc{box-shadow:none; break-inside:avoid}
}

/* ─── Mobile ─────────────────────────────────────────────────────────── */
.backdrop{display:none; position:fixed; inset:var(--header-h) 0 0 0; background:rgba(0,0,0,.4); z-index:35}
@media(max-width:900px){
  .sidebar{transform:translateX(-100%); transition:transform .2s; box-shadow:var(--shadow)}
  .sidebar.open{transform:translateX(0)}
  main.content{margin-left:0; padding:28px 20px 80px}
  .hamburger{display:grid}
  .backdrop.open{display:block}
  .calc-grid{grid-template-columns:1fr}
  .stackrow{grid-template-columns:1fr auto; row-gap:6px}
}

/* ─── KaTeX ──────────────────────────────────────────────────────────── */
.katex{font-size:1.05em}
.katex-display{margin:10px 0; overflow-x:auto}