:root{
  --brand:#0b3d6b; --brand-2:#12507f; --ink:#16222e; --muted:#5a6b7c;
  --bg:#f5f7fa; --card:#ffffff; --line:#dbe4ee; --accent:#f0ad4e; --good:#1a7f37;
  --radius:14px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;font-family:"Segoe UI",system-ui,-apple-system,Arial,sans-serif;color:var(--ink);background:var(--bg);line-height:1.65;font-size:16px}
img,svg{max-width:100%;height:auto}
a{color:var(--brand-2)}
.container{max-width:1100px;margin:0 auto;padding:0 20px}

.site-header{background:linear-gradient(135deg,#0b3d6b 0%,#12507f 60%,#1a6aa8 100%);color:#fff}
.site-header .inner{display:flex;align-items:center;justify-content:space-between;gap:16px;padding:14px 0;flex-wrap:wrap}
.brand{display:flex;align-items:center;gap:10px;color:#fff;text-decoration:none;font-weight:700;font-size:18px;letter-spacing:.3px}
.brand .logo{width:30px;height:30px;border-radius:8px;background:#fff;color:var(--brand);display:flex;align-items:center;justify-content:center;font-weight:800;font-size:13px}
.site-nav{display:flex;gap:6px;flex-wrap:wrap;align-items:center}
.site-nav a{color:#dbe9f7;text-decoration:none;padding:7px 12px;border-radius:8px;font-size:14.5px}
.site-nav a:hover{background:rgba(255,255,255,.14);color:#fff}
.site-nav a.active{background:rgba(255,255,255,.2);color:#fff;font-weight:600}
.lang-btn{background:rgba(255,255,255,.16);color:#fff;border:1px solid rgba(255,255,255,.45);border-radius:8px;padding:6px 14px;font-size:14px;font-weight:700;cursor:pointer;margin-left:6px}
.lang-btn:hover{background:rgba(255,255,255,.28)}

.hero{background:linear-gradient(135deg,#0b3d6b,#1a6aa8);color:#fff;padding:54px 0 66px}
.hero h1{margin:0 0 10px;font-size:34px;line-height:1.25}
.hero p{margin:0;color:#d7e6f5;font-size:17px;max-width:780px}

.section-title{font-size:21px;color:var(--brand);margin:34px 0 14px;padding-bottom:8px;border-bottom:2px solid #e3ebf4}
.cards{display:grid;grid-template-columns:repeat(auto-fit,minmax(290px,1fr));gap:18px;margin:-38px 0 30px}
.cards.in-section{margin:0 0 30px}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:22px;box-shadow:0 10px 24px rgba(11,61,107,.08);display:flex;flex-direction:column;gap:10px}
.card .tag{font-size:12px;font-weight:700;letter-spacing:.6px;text-transform:uppercase;color:var(--brand-2)}
.card h2{margin:0;font-size:19px;line-height:1.35}
.card h2 a{color:var(--ink);text-decoration:none}
.card h2 a:hover{color:var(--brand-2)}
.card p{margin:0;color:var(--muted);font-size:14.5px}
.card .meta-line{font-size:12.5px;color:#8296a8}
.card a.more{margin-top:auto;font-weight:600;text-decoration:none}
.card a.more:hover{text-decoration:underline}

.article{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:30px 34px;margin:28px 0 40px;box-shadow:0 10px 24px rgba(11,61,107,.06)}
.article h1{margin:0 0 6px;color:var(--brand);font-size:28px;line-height:1.3}
.lead{color:var(--muted);margin:0 0 6px;font-size:15.5px}
.meta{color:#8296a8;font-size:13.5px;margin:0 0 18px}
.article h2{color:var(--brand);font-size:19px;margin:34px 0 10px;padding-bottom:6px;border-bottom:2px solid #e3ebf4}
.article h3{color:var(--brand-2);font-size:16.5px;margin:22px 0 8px}
.article p{margin:0 0 12px}
.article ul,.article ol{margin:0 0 14px;padding-left:22px}
.article li{margin-bottom:6px}
.note{background:#fff8e1;border-left:4px solid var(--accent);border-radius:8px;padding:12px 16px;margin:16px 0;font-size:14.5px}
.tablewrap{overflow-x:auto;margin:0 0 16px}
table{border-collapse:collapse;width:100%;min-width:640px}
th,td{border:1px solid var(--line);padding:9px 12px;text-align:left;vertical-align:top;font-size:14.5px}
th{background:#eef4fb;font-weight:700}
tr:nth-child(even) td{background:#fafcfe}
.good{color:var(--good);font-weight:600}
.diagram{margin:18px 0;border:1px solid var(--line);border-radius:10px;overflow:hidden;background:#fff}
.diagram svg{display:block;width:100%;height:auto}
.diagram.zoomable{cursor:zoom-in;position:relative;transition:border-color .15s,box-shadow .15s}
.diagram.zoomable:hover{border-color:#7fa8cc;box-shadow:0 6px 18px rgba(11,61,107,.12)}
.diagram.zoomable:focus{outline:3px solid rgba(26,106,168,.35);outline-offset:2px}
.diagram.zoomable::after{content:"\2922";position:absolute;top:8px;right:10px;font-size:15px;line-height:1;color:var(--brand);background:rgba(255,255,255,.9);border:1px solid var(--line);border-radius:6px;padding:3px 7px;pointer-events:none;opacity:.8}

/* Diagram lightbox */
.dlg-overlay{position:fixed;top:0;right:0;bottom:0;left:0;background:rgba(8,20,32,.86);z-index:1000;display:flex;align-items:center;justify-content:center;padding:20px}
.dlg-inner{background:#fff;border-radius:12px;box-shadow:0 24px 60px rgba(0,0,0,.5);max-width:96vw;max-height:92vh;overflow:auto;padding:10px}
.dlg-inner svg{display:block;width:100%;height:auto}
.dlg-close{position:absolute;top:16px;right:18px;width:44px;height:44px;border:0;border-radius:50%;background:#fff;color:var(--brand);font-size:24px;line-height:1;font-weight:700;cursor:pointer;box-shadow:0 6px 18px rgba(0,0,0,.35)}
.dlg-close:hover{background:#eef6ff}
.crumb{font-size:13.5px;margin:18px 0 -14px;color:var(--muted)}
.crumb a{text-decoration:none}

/* CTA */
.cta{background:#eef6ff;border:1px solid #cfe0f0;border-radius:12px;padding:18px 20px;margin:30px 0 0;display:flex;justify-content:space-between;gap:12px;align-items:center;flex-wrap:wrap}
.cta b{color:var(--brand);font-size:16px}
.cta p{margin:2px 0 0;color:var(--muted);font-size:14px}
.btn{display:inline-block;background:var(--brand);color:#fff;border:0;border-radius:8px;padding:10px 22px;font-size:15px;cursor:pointer;font-weight:600;text-decoration:none;text-align:center;transition:background .15s}
.btn:hover{background:var(--brand-2);color:#fff}
.btn[disabled]{opacity:.6;cursor:not-allowed}

/* ============ Comments (forum style) ============ */
.comments{margin-top:40px;border-top:2px solid #e3ebf4;padding-top:20px}
.comments-head{display:flex;align-items:center;gap:10px;margin-bottom:16px}
.comments-head h2{color:var(--brand);font-size:19px;margin:0}
.comment-count{color:#8296a8;font-size:15px;font-weight:600}
.composer{background:#f8fafc;border:1px solid var(--line);border-radius:12px;padding:14px;margin-bottom:8px}
.composer textarea{display:block;width:100%;border:1px solid var(--line);border-radius:8px;padding:10px 12px;font:inherit;font-size:14.5px;min-height:88px;resize:vertical;background:#fff;color:var(--ink)}
.composer textarea:focus,.composer input:focus,.field input:focus,.field select:focus,.field textarea:focus{outline:none;border-color:#7fa8cc;box-shadow:0 0 0 3px rgba(26,106,168,.12)}
.composer-row{display:flex;gap:10px;margin-top:10px;align-items:center;flex-wrap:wrap}
.composer-row input{flex:1;min-width:180px;border:1px solid var(--line);border-radius:8px;padding:10px 12px;font:inherit;font-size:14.5px;background:#fff;color:var(--ink)}
.composer .hint{margin:10px 0 0;font-size:13px;color:#8296a8}
.comment-list{margin-top:10px}
.comment{display:flex;gap:12px;padding:14px 2px;border-bottom:1px solid var(--line)}
.comment:last-child{border-bottom:0}
.avatar{width:40px;height:40px;border-radius:50%;background:linear-gradient(135deg,#0b3d6b,#1a6aa8);color:#fff;display:flex;align-items:center;justify-content:center;font-weight:700;font-size:16px;flex:0 0 40px;text-transform:uppercase}
.comment-main{flex:1;min-width:0}
.comment-top{display:flex;align-items:baseline;gap:8px;flex-wrap:wrap}
.comment .who{font-weight:700;font-size:14.5px}
.comment .when{color:#8296a8;font-size:12.5px}
.comment .text{margin-top:4px;white-space:pre-wrap;font-size:14.5px}
.msg-line{margin:8px 0 0;font-size:14px}
.msg-ok{color:var(--good);font-weight:600}
.msg-err{color:#c0392b;font-weight:600}
.hp{position:absolute;left:-9999px;width:1px;height:1px;overflow:hidden}

/* ============ Contact (JLCPCB style) ============ */
.contact-hero h1{color:var(--brand);font-size:28px;margin:22px 0 6px}
.contact-hero p{color:var(--muted);margin:0 0 22px;max-width:760px}
.contact-grid{display:grid;grid-template-columns:1.35fr .65fr;gap:22px;align-items:start;margin-bottom:40px}
.contact-card{background:#fff;border:1px solid var(--line);border-radius:14px;padding:26px 28px;box-shadow:0 10px 24px rgba(11,61,107,.06)}
.contact-card h2{margin:0 0 4px;font-size:19px;color:var(--brand)}
.form-note{font-size:13px;color:#8296a8;margin:0 0 16px}
.form-note .req{color:#c0392b;font-weight:700}
.field{margin-bottom:14px}
.field label{display:block;font-size:13.5px;font-weight:600;color:#37475a;margin-bottom:5px}
.field .req{color:#c0392b}
.field input,.field select,.field textarea{width:100%;padding:10px 12px;border:1px solid var(--line);border-radius:8px;font:inherit;font-size:14.5px;background:#fff;color:var(--ink)}
.field textarea{min-height:140px;resize:vertical}
.field input[type=checkbox]{width:auto}
.row2{display:grid;grid-template-columns:1fr 1fr;gap:14px}
.info-col .info-box{background:#f8fafc;border:1px solid var(--line);border-radius:12px;padding:18px 20px;font-size:14.5px}
.info-col .info-box + .info-box{margin-top:14px}
.info-box h3{margin:0 0 8px;color:var(--brand-2);font-size:16px}
.info-box ul{margin:0;padding-left:18px;color:var(--muted)}
.info-box li{margin-bottom:5px}
form.cform{display:grid;gap:10px;margin-top:16px}
form.cform input,form.cform textarea,form.cform select{width:100%;padding:10px 12px;border:1px solid var(--line);border-radius:8px;font:inherit;font-size:14.5px;background:#fff;color:var(--ink)}
form.cform textarea{min-height:110px;resize:vertical}

.site-footer{background:#0b3d6b;color:#cfe0f0;margin-top:20px}
.site-footer .inner{padding:26px 0;display:flex;justify-content:space-between;gap:14px;flex-wrap:wrap;font-size:13.5px}
.site-footer a{color:#fff}

@media (max-width:640px){
  .hero{padding:40px 0 58px}
  .hero h1{font-size:26px}
  .article{padding:20px 18px}
  .article h1{font-size:23px}
  .row2{grid-template-columns:1fr}
  .contact-grid{grid-template-columns:1fr}
  .contact-card{padding:20px 18px}
}

/* ============ Article sidebar (menu dọc) ============ */
.article-side{margin-top:20px}
.side-box{background:#fff;border:1px solid var(--line);border-radius:14px;padding:16px 18px;box-shadow:0 6px 16px rgba(11,61,107,.05)}
.side-box + .side-box{margin-top:14px}
.side-box h3{margin:0 0 10px;font-size:14px;color:var(--brand);text-transform:uppercase;letter-spacing:.5px}
.side-nav{display:flex;flex-direction:column;gap:4px}
.side-nav a{display:block;padding:9px 10px;border-radius:8px;text-decoration:none;color:var(--ink);font-size:14.5px;line-height:1.4;border:1px solid transparent}
.side-nav a:hover{background:#f0f6fc;color:var(--brand-2)}
.side-nav a.active{background:#eef6ff;border-color:#cfe0f0;color:var(--brand);font-weight:600}
.side-tag{display:block;font-size:11px;color:#8296a8;text-transform:uppercase;letter-spacing:.5px;margin-bottom:2px}
.side-note{margin:0 0 10px;color:var(--muted);font-size:13.5px}
.side-cta{display:block;width:100%}

@media (min-width:901px){
  main.container:has(> .article-side){
    display:grid;
    grid-template-columns:minmax(0,1fr) 290px;
    gap:22px;
    align-items:start;
  }
  main.container:has(> .article-side) > .crumb{grid-column:1/-1}
  main.container:has(> .article-side) > .article{margin:28px 0 40px}
  main.container:has(> .article-side) > .article-side{grid-column:2;position:sticky;top:16px;margin-top:28px}
}