/* Roji Unit Converter with Dimensional Analysis.
   Layout: Roji brand header, two tabs. "Show the chain" has setup on the left and the worked chain on the right
   (stacked on phones). "Build it myself" is one column: problem, chain, answer. */
:root{
  --navy:#1D5B8D; --sky:#0B7CC9; --green:#3CC47C; --green-ink:#1E8A52;
  --bg:#EEF5FB; --surface:#FFFFFF; --ink:#16324A; --muted:#557089; --line:#CFE0EE; --field:#F7FBFE; --tint:#E3EFF9;
  --on-navy:#FFFFFF; --warn-bg:#FFF1CC; --warn-ink:#7A5400; --ok-bg:#DDF5E8; --ok-ink:#15693F; --err-ink:#A3261B;
  --x1:#D6402F; --x2:#7A4BD1; --x3:#C46A00; --x4:#0E8F8A; --gone:#7F97AC;
  --title-fill:#0B7CC9; --title-stroke:#12344F;
  --shadow:0 1px 0 #d7e6f2, 0 10px 30px -18px rgba(29,91,141,.45);
  --f-display:"Luckiest Guy","Arial Rounded MT Bold","Trebuchet MS",sans-serif;
  --f-body:"Nunito",system-ui,-apple-system,"Segoe UI",sans-serif;
  color-scheme:light;
}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){
  --bg:#0E1B27; --surface:#15283A; --ink:#E6F0F8; --muted:#9BB3C8; --line:#27425A; --field:#10202F; --tint:#1B3247;
  --navy:#5CADE2; --sky:#5CADE2; --green-ink:#5FD897; --on-navy:#06121C;
  --warn-bg:#3B3013; --warn-ink:#F4CF6E; --ok-bg:#153B2A; --ok-ink:#7FE3AE; --err-ink:#FF9C8F;
  --x1:#FF8A7A; --x2:#B79CFF; --x3:#F4B860; --x4:#5FD6CF; --gone:#7C93A8;
  --title-fill:#5CADE2; --title-stroke:#06121C; --shadow:0 12px 30px -20px rgba(0,0,0,.8); color-scheme:dark}}
:root[data-theme="dark"]{
  --bg:#0E1B27; --surface:#15283A; --ink:#E6F0F8; --muted:#9BB3C8; --line:#27425A; --field:#10202F; --tint:#1B3247;
  --navy:#5CADE2; --sky:#5CADE2; --green-ink:#5FD897; --on-navy:#06121C;
  --warn-bg:#3B3013; --warn-ink:#F4CF6E; --ok-bg:#153B2A; --ok-ink:#7FE3AE; --err-ink:#FF9C8F;
  --x1:#FF8A7A; --x2:#B79CFF; --x3:#F4B860; --x4:#5FD6CF; --gone:#7C93A8;
  --title-fill:#5CADE2; --title-stroke:#06121C; --shadow:0 12px 30px -20px rgba(0,0,0,.8); color-scheme:dark}

*{box-sizing:border-box}
[hidden]{display:none!important}
body{margin:0;background:var(--bg);color:var(--ink);font-family:var(--f-body);font-size:16px;line-height:1.5;-webkit-text-size-adjust:100%}
.wrap{max-width:1180px;margin:0 auto;padding-inline:clamp(16px,3vw,32px);padding-block:12px 40px}
button,input,select,textarea{font-family:inherit}
:focus-visible{outline:3px solid var(--green);outline-offset:2px}
p{margin:0}

/* ---------- brand header (same on every Roji tool) ---------- */
.brandbar{display:flex;justify-content:space-between;align-items:center;gap:12px;font-weight:800;color:var(--navy);font-size:.9rem}
.brandbar a{color:inherit;text-decoration:none}
.brandbar .kit{letter-spacing:.08em;text-transform:uppercase;font-size:.72rem;color:var(--muted)}
.hero{display:flex;align-items:center;margin-block:4px 10px}
.hero-text{flex:1;min-width:0;padding-bottom:clamp(8px,2vw,20px)}
.eyebrow{font-weight:800;color:var(--green-ink);letter-spacing:.08em;text-transform:uppercase;font-size:.78rem}
h1{font-family:var(--f-display);font-weight:400;font-size:clamp(1.9rem,5.4vw,3.4rem);line-height:.98;margin:4px 0 10px;
  color:var(--title-fill);-webkit-text-stroke:2px var(--title-stroke);paint-order:stroke fill;letter-spacing:.01em;text-wrap:balance;text-shadow:0 3px 0 var(--title-stroke)}
.tagline{color:var(--muted);font-weight:700;max-width:56ch}
.roji{flex:0 0 auto;width:clamp(96px,20vw,200px);display:block}
.roji img{width:100%;height:auto;display:block;filter:drop-shadow(0 8px 12px rgba(18,52,79,.18))}

/* ---------- tabs ---------- */
.tabs{display:flex;gap:6px;background:var(--tint);border-radius:16px;padding:6px;margin-bottom:16px;max-width:520px}
.tabs button{flex:1;min-width:0;min-height:48px;border:0;border-radius:11px;background:transparent;color:var(--ink);font-weight:800;font-size:1rem;cursor:pointer;padding:8px 10px}
.tabs button[aria-selected="true"]{background:var(--navy);color:var(--on-navy)}

.example{display:flex;flex-wrap:wrap;gap:8px 14px;align-items:center;justify-content:space-between;background:var(--warn-bg);color:var(--warn-ink);
  border-radius:14px;padding:10px 14px;font-weight:700;margin-bottom:16px}

/* ---------- layout ---------- */
.app{display:grid;grid-template-columns:minmax(0,360px) minmax(0,1fr);gap:20px;align-items:start}
@media (max-width:900px){.app{grid-template-columns:minmax(0,1fr)}}
.panel{background:var(--surface);border-radius:18px;box-shadow:var(--shadow);padding:6px 20px 20px;min-width:0}
.grp{padding-top:14px;display:grid;gap:10px}
.grp+.grp{border-top:2px dashed var(--line);margin-top:16px}
.grp h2,.card-h{font-size:.78rem;text-transform:uppercase;letter-spacing:.08em;color:var(--green-ink);margin:0;font-weight:800}
label{display:grid;gap:4px;font-size:.85rem;font-weight:800;color:var(--muted)}
.hint{font-weight:600;font-size:.85rem;color:var(--muted);max-width:65ch}
.lbl{font-size:.85rem;font-weight:800;color:var(--muted)}
input,select,textarea{font-size:1rem;font-weight:700;color:var(--ink);background:var(--field);border:2px solid var(--line);border-radius:10px;padding:9px 10px;width:100%;min-width:0;min-height:44px}
input:focus,select:focus{border-color:var(--sky)}
.row{display:grid;grid-template-columns:repeat(auto-fit,minmax(120px,1fr));gap:10px;align-items:end}
.check{display:flex;align-items:center;gap:10px;font-weight:700;color:var(--ink);font-size:.95rem;min-height:44px}
.check input{width:22px;height:22px;min-height:0;flex:none;accent-color:var(--green)}
.seg{display:flex;flex-wrap:wrap;gap:6px}
.seg button{font-size:.9rem;font-weight:800;border:2px solid var(--line);background:var(--surface);color:var(--ink);border-radius:999px;padding:8px 13px;min-height:44px;cursor:pointer}
.seg button[aria-pressed="true"]{background:var(--navy);color:var(--on-navy);border-color:var(--navy)}

.btn{display:inline-flex;align-items:center;justify-content:center;font-size:.95rem;font-weight:800;border:2px solid var(--navy);background:var(--navy);color:var(--on-navy);
  border-radius:12px;padding:9px 16px;min-height:44px;cursor:pointer;text-decoration:none}
.btn.ghost{background:transparent;color:var(--navy)}
.btn.small{font-size:.88rem;padding:6px 12px;justify-self:start}
.actions{display:flex;flex-wrap:wrap;gap:8px}

.fact-form{display:grid;grid-template-columns:minmax(0,3fr) minmax(0,4fr) auto minmax(0,3fr) minmax(0,4fr);gap:6px;align-items:center}
.fact-form input{padding-inline:6px}
.fact-form .eq{font-weight:800;color:var(--muted)}
.myfacts{list-style:none;margin:0;padding:0;display:grid;gap:6px}
.myfacts:empty{display:none}
.myfacts li{display:flex;align-items:center;justify-content:space-between;gap:8px;background:var(--tint);border-radius:10px;padding:4px 4px 4px 12px;font-weight:800}
.myfacts button{border:0;background:transparent;color:var(--navy);font-weight:800;min-height:40px;min-width:44px;cursor:pointer;border-radius:8px}
.err{color:var(--err-ink);font-weight:800;font-size:.9rem}
.err:empty{display:none}
.err.big{background:var(--warn-bg);color:var(--warn-ink);border-radius:12px;padding:10px 14px;font-size:1rem}

/* ---------- result side ---------- */
.result,.build{min-width:0;display:grid;gap:14px}
.build{max-width:820px}
.card{background:var(--surface);border-radius:18px;box-shadow:var(--shadow);padding:16px 20px 20px;min-width:0;display:grid;gap:12px}
.card-h{display:flex;align-items:center;gap:8px}
.card-h .num{display:inline-grid;place-items:center;width:24px;height:24px;border-radius:50%;background:var(--navy);color:var(--on-navy);font-size:.85rem;letter-spacing:0}

/* the chain: fractions side by side, wrapping on narrow screens */
.chain{display:flex;flex-wrap:wrap;align-items:center;gap:14px 8px;padding-block:6px;font-variant-numeric:tabular-nums}
.slot{display:grid;justify-items:center;gap:6px;min-width:0}
.frac{display:inline-grid;text-align:center;font-weight:800;font-size:clamp(1rem,3.6vw,1.2rem);line-height:1.25}
.frac .t,.frac .b{padding:3px 8px;white-space:nowrap}
.frac .t{border-bottom:3px solid var(--ink)}
.pw{display:inline-flex;align-items:stretch}
.pw .frac{border-inline:3px solid var(--ink);border-radius:14px/50%;padding-inline:2px}
.pw sup{font-weight:800;font-size:1rem;align-self:flex-start;margin-left:2px;line-height:1}
.op{font-weight:800;font-size:1.3rem;color:var(--muted)}
.u{position:relative;display:inline-block}
.u.x{color:var(--gone)}
.u.x::after{content:"";position:absolute;left:-3px;right:-3px;top:50%;border-top:3px solid var(--x1);transform:rotate(-16deg)}
.u.x.p2::after{border-color:var(--x2)} .u.x.p3::after{border-color:var(--x3)} .u.x.p4::after{border-color:var(--x4)}
.u.keep{color:var(--green-ink)}
.slot-btns{display:flex;gap:4px}
.slot-btns button{border:2px solid var(--line);background:var(--surface);color:var(--navy);border-radius:999px;font-weight:800;font-size:.8rem;min-height:36px;min-width:44px;padding:4px 10px;cursor:pointer}
.start-tag{font-size:.72rem;font-weight:800;text-transform:uppercase;letter-spacing:.06em;color:var(--muted);min-height:36px;display:grid;place-items:center}

.multiply{font-weight:800;font-size:1.05rem;color:var(--muted);overflow-wrap:anywhere;font-variant-numeric:tabular-nums}
.answer{background:var(--navy);color:var(--on-navy);border-radius:14px;padding:12px 16px;display:grid;gap:2px}
.answer .big{font-family:var(--f-display);font-size:clamp(1.7rem,7vw,2.6rem);line-height:1.05;overflow-wrap:anywhere;padding-top:.1em}
.answer .small{font-weight:700;font-size:.95rem;opacity:.92}
.note{background:var(--warn-bg);color:var(--warn-ink);border-radius:10px;padding:8px 12px;font-weight:700;font-size:.9rem}
.steps{margin:0;padding-left:1.4em;display:grid;gap:8px;font-weight:600;max-width:68ch}
.steps li::marker{font-weight:800;color:var(--navy)}

.tools{display:grid;gap:8px}
.toast:empty{display:none}
.toast{background:var(--ok-bg);color:var(--ok-ink);border-radius:10px;padding:8px 12px;font-weight:700;font-size:.9rem}
.copybox{min-height:120px;font-size:.85rem;font-weight:600}
.how{background:var(--surface);border-radius:14px;padding:12px 16px;box-shadow:var(--shadow)}
.how summary{cursor:pointer;font-weight:800;color:var(--navy);min-height:28px}
.how p{margin-top:8px;max-width:65ch}
.how ul{margin:8px 0 0;padding-left:1.2em;display:grid;gap:4px;max-width:65ch}

/* ---------- build it myself ---------- */
.story{font-size:1.15rem;font-weight:800;max-width:60ch}
.left{font-weight:800}
.left b{background:var(--tint);border-radius:8px;padding:2px 8px;white-space:nowrap}
.left.match b{background:var(--ok-bg);color:var(--ok-ink)}
.tray{display:flex;flex-wrap:wrap;gap:8px}
.tray button{border:2px solid var(--line);background:var(--field);color:var(--ink);border-radius:12px;font-weight:800;font-size:.98rem;min-height:48px;padding:6px 12px;cursor:pointer;display:grid;text-align:left}
.tray button small{font-weight:700;color:var(--muted);font-size:.74rem}
.tray button[aria-pressed="true"]{border-color:var(--green);background:var(--ok-bg);color:var(--ok-ink)}
.tray button[aria-pressed="true"] small{color:inherit}
.feedback:empty{display:none}
.feedback{border-radius:12px;padding:10px 14px;font-weight:700;background:var(--warn-bg);color:var(--warn-ink);max-width:65ch}
.feedback.good{background:var(--ok-bg);color:var(--ok-ink)}
.step.locked{opacity:.7}
.answer-row{grid-template-columns:minmax(0,1fr) auto auto;align-items:end}
.unit-tag{font-weight:800;font-size:1.05rem;min-height:44px;display:grid;place-items:center}
@media (max-width:480px){.answer-row{grid-template-columns:minmax(0,1fr) auto}.answer-row .btn{grid-column:1/-1}}

footer.site{margin-top:28px;display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap;color:var(--muted);font-size:.85rem;font-weight:700}
footer.site span{max-width:70ch}
footer.site a{color:var(--navy)}
@media (prefers-reduced-motion:reduce){*{transition:none!important;animation:none!important}}
#bChain{align-items:flex-start}
#bChain .op{margin-top:14px}