:root{--ink:#0E2F6B;--ink-deep:#0A2352;--sun:#FFCD1C;--sun-soft:#FFF3C4;--desk:#EEF3FB;--paper:#FFFFFF;--pen:#D8342B;--text:#1D2A44;--muted:#55627D;--line:#CFD9EA}
*{box-sizing:border-box}
body{margin:0;font-family:"Sarabun","Leelawadee UI","Tahoma",sans-serif;font-size:18px;line-height:1.8;color:var(--text);background:var(--paper)}
h1,h2,h3{font-family:"Mitr","Sarabun",sans-serif;color:var(--ink);font-weight:500;line-height:1.35;margin:0;text-wrap:balance}
a{color:var(--ink)}
a:focus-visible{outline:3px solid var(--sun);outline-offset:3px;border-radius:6px}
img{max-width:100%}
.wrap{max-width:760px;margin:0 auto;padding-left:max(20px,env(safe-area-inset-left,0px));padding-right:max(20px,env(safe-area-inset-right,0px))}
.top{background:var(--ink-deep)}
.top .wrap{display:flex;align-items:center;gap:12px;padding-block:12px;max-width:1080px}
.logo{display:flex;align-items:center;gap:10px;text-decoration:none;font:500 20px "Mitr",sans-serif;color:#fff}
.logo img{width:40px;height:40px;border-radius:50%;border:2px solid var(--sun)}
.top nav{margin-left:auto;display:flex;gap:16px;font-size:15px}
.top nav a{color:#fff;text-decoration:none;opacity:.9}
.top nav a:hover{text-decoration:underline}
main{padding-block:28px 56px}
.crumb{font-size:14px;color:var(--muted);margin-bottom:10px}
.crumb a{color:var(--muted)}
article h1{font-size:clamp(26px,5vw,36px)}
.meta{font-size:14px;color:var(--muted);margin:10px 0 22px}
article h2{font-size:23px;margin:30px 0 10px}
article h3{font-size:19px;margin:22px 0 8px}
article p{margin:0 0 14px}
article ul,article ol{padding-left:24px;margin:0 0 14px}
.box{background:var(--desk);border:1px solid var(--line);border-radius:14px;padding:14px 18px;margin:16px 0}
.box.sun{background:var(--sun-soft);border-color:var(--sun)}
.math{font:500 22px "Mitr",sans-serif;color:var(--ink);letter-spacing:.02em}
.ans{font-weight:600;color:#1E7F52}
.cta{background:var(--ink-deep);color:#fff;border-radius:16px;padding:18px 20px;margin-top:30px;display:grid;gap:10px}
.cta h2{color:var(--sun);font-size:21px;margin:0}
.cta p{margin:0}
.cta a.btn{justify-self:start;background:var(--sun);color:#4A3800;text-decoration:none;font:500 17px "Mitr",sans-serif;border-radius:10px;padding:9px 18px}
.tags{display:flex;flex-wrap:wrap;gap:8px;margin-top:22px}
.tags span{background:var(--desk);border-radius:999px;padding:2px 12px;font-size:14px;color:var(--ink)}
.list{display:grid;gap:14px;margin-top:20px}
.list a{display:grid;gap:4px;text-decoration:none;border:1px solid var(--line);border-radius:14px;padding:14px 18px;background:var(--paper)}
.list a:hover{border-color:var(--ink)}
.list b{font:500 19px/1.4 "Mitr",sans-serif;color:var(--ink)}
.list span{font-size:15px;color:var(--muted)}
footer{border-top:1px solid var(--line);font-size:14px;color:var(--muted);padding-block:18px}