.rs-hero{background:linear-gradient(180deg,#f2f6fb 0%,#fff 100%);padding:56px 0 40px}
.rs-hero .lead{max-width:640px}
.rs-sec{padding:64px 0}
.rs-sec.alt{background:var(--bg2);border-block:1px solid var(--line)}
.rs-grid{display:grid;grid-template-columns:1fr 1fr;gap:48px;align-items:center}
.rs-text h2{text-align:right;font-size:32px;margin:10px 0 14px}
.rs-text p{font-size:17.5px;line-height:1.75;color:var(--text);margin-bottom:12px}
.step-num{display:inline-flex;width:40px;height:40px;border-radius:50%;background:var(--blue);color:#fff;align-items:center;justify-content:center;font-weight:700;font-size:19px}
.rs-steps{padding-right:22px;margin:6px 0 14px;display:grid;gap:8px;font-size:17px;line-height:1.7}
.hint{background:var(--blue-soft);border-radius:12px;padding:12px 16px;font-size:16px!important}
h2.center{text-align:center}

/* on-screen sizer */
.sizer{background:#fff;border:1px solid var(--line);border-radius:22px;padding:20px;box-shadow:var(--shadow)}
.sizer-tabs{display:grid;grid-template-columns:1fr 1fr;background:var(--stage);border-radius:999px;padding:4px;margin-bottom:14px}
.sz-tab{border:0;background:transparent;border-radius:999px;padding:9px 6px;font-size:15px;cursor:pointer;color:var(--muted)}
.sz-tab.on{background:#fff;color:var(--ink);font-weight:600;box-shadow:0 1px 4px rgba(0,0,0,.1)}
.sizer-stage{position:relative;background:var(--stage);border-radius:16px;height:300px;display:flex;align-items:center;justify-content:center;overflow:hidden}
#sz-svg{position:absolute;inset:0;width:100%;height:100%}
.sz-caption{position:absolute;bottom:10px;left:0;right:0;text-align:center;font-size:14px;color:var(--muted)}
.sz-label{display:block;font-size:14px;color:var(--muted);margin:14px 0 6px}
.sz-control{display:flex;align-items:center;gap:10px;margin-bottom:14px}
.sz-control input{flex:1;-webkit-appearance:none;appearance:none;height:6px;border-radius:3px;background:var(--line);direction:ltr}
.sz-control input::-webkit-slider-thumb{-webkit-appearance:none;width:26px;height:26px;border-radius:50%;background:#fff;border:3px solid var(--blue)}
.sz-control input::-moz-range-thumb{width:22px;height:22px;border-radius:50%;background:#fff;border:3px solid var(--blue)}
.sz-step{width:40px;height:40px;border-radius:50%;border:1px solid var(--line2);background:#fff;font-size:22px;line-height:1;cursor:pointer;flex:none}
.sz-result{display:grid;grid-template-columns:repeat(4,1fr);gap:8px;margin-top:14px}
.sz-result div{background:var(--stage);border-radius:12px;padding:10px;text-align:center}
.sz-result span{display:block;font-size:12.5px;color:var(--muted)}
.sz-result b{font-family:var(--head);font-size:24px;color:var(--ink);direction:ltr;unicode-bidi:isolate}

/* string calc */
.circ-calc{background:#fff;border:1px solid var(--line);border-radius:14px;padding:14px 16px;margin:8px 0 14px}
.circ-calc label{font-size:14px;color:var(--muted)}
.circ-row{display:flex;gap:12px;align-items:center;margin-top:6px}
.circ-row input{width:130px;font-size:22px;font-weight:700;padding:8px 10px;border:2px solid var(--line2);border-radius:10px;direction:ltr;text-align:right}
.circ-row input:focus{outline:none;border-color:var(--blue)}
.circ-out{font-size:17px;color:var(--ink);font-weight:500}

/* animation */
.anim-card{background:#fff;border:1px solid var(--line);border-radius:22px;padding:16px;box-shadow:var(--shadow)}
.string-anim{width:100%;height:auto;display:block}
.anim-label{font:600 14px Heebo,sans-serif;fill:var(--ink);opacity:0;animation:fadeIn 6s infinite}
.wrap-front,.wrap-back{stroke-dasharray:90;stroke-dashoffset:90;animation:wrapIn 6s infinite}
.wrap-back{animation-delay:.15s}
.mark{opacity:0;animation:markIn 6s infinite}
.ruler{opacity:0;animation:rulerIn 6s infinite}
.laid{stroke-dasharray:215;stroke-dashoffset:215;animation:lay 6s infinite}
.mark2{opacity:0;animation:mark2 6s infinite}
@keyframes wrapIn{0%{stroke-dashoffset:90}20%,55%{stroke-dashoffset:0}65%,100%{stroke-dashoffset:90}}
@keyframes markIn{0%,25%{opacity:0}30%,55%{opacity:1}65%,100%{opacity:0}}
@keyframes rulerIn{0%,55%{opacity:0}62%,95%{opacity:1}100%{opacity:0}}
@keyframes lay{0%,60%{stroke-dashoffset:215}80%,95%{stroke-dashoffset:0}100%{stroke-dashoffset:215}}
@keyframes mark2{0%,78%{opacity:0}82%,95%{opacity:1}100%{opacity:0}}
@keyframes fadeIn{0%,82%{opacity:0}86%,95%{opacity:1}100%{opacity:0}}
@media (prefers-reduced-motion:reduce){.wrap-front,.wrap-back,.laid{animation:none;stroke-dashoffset:0}.mark,.ruler,.mark2,.anim-label{animation:none;opacity:1}}

/* tips */
.tips{display:grid;grid-template-columns:repeat(3,1fr);gap:18px;margin-top:30px}
.tip{background:#fff;border:1px solid var(--line);border-radius:16px;padding:20px}
.tip b{font-family:var(--head);font-size:18px;color:var(--ink)}
.tip p{color:var(--muted);margin-top:6px;line-height:1.65}

/* chart */
.table-wrap{overflow-x:auto;background:#fff;border:1px solid var(--line);border-radius:16px}
.size-table{width:100%;border-collapse:collapse;font-size:16px;text-align:center}
.size-table th{background:var(--ink);color:#fff;padding:12px 8px;font-weight:600;font-size:14.5px}
.size-table td{padding:10px 8px;border-top:1px solid var(--line);direction:ltr}
.size-table tr.pop td{background:#f2f7ff;font-weight:600}

/* faq */
.faq{max-width:780px}
.faq details{background:#fff;border:1px solid var(--line);border-radius:14px;padding:14px 18px;margin-top:12px}
.faq summary{cursor:pointer;font-weight:600;font-size:17.5px;color:var(--ink)}
.faq p{margin-top:10px;line-height:1.75;color:var(--text)}

@media (max-width:1000px){.rs-grid{grid-template-columns:1fr}.tips{grid-template-columns:1fr 1fr}}
@media (max-width:600px){
  .rs-sec{padding:44px 0}
  .rs-text h2{font-size:25px}
  .tips{grid-template-columns:1fr}
  .sizer-stage{height:260px}
  .sz-result b{font-size:20px}
  .hero-btns .btn{flex:1 1 auto}
}