/* ============ MathSolver Archive — Design System ============ */
:root{
  --brand-900:#0E2A5C;
  --brand-700:#1B4FA0;
  --brand-500:#2E6FD0;
  --brand-300:#7EA6E0;
  --brand-100:#DCE9FB;
  --brand-050:#F2F7FE;
  --accent-500:#3FBFA0;
  --accent-600:#2FA98C;
  --accent-050:#DCF3EC;
  --ink-900:#16233A;
  --ink-700:#33415C;
  --ink-500:#5B6B80;
  --ink-400:#7C8BA0;
  --bg:#F7FAFF;
  --surface:#FFFFFF;
  --surface-soft:#EEF2F8;
  --line:#E3EAF3;
  --amber:#F0A93B;
  --amber-050:#FDF3E3;
  --coral:#E4685A;
  --coral-050:#FCEAE7;
  --violet:#7A6FD0;
  --radius-sm:8px;
  --radius-md:12px;
  --radius-lg:20px;
  --radius-xl:28px;
  --shadow-sm:0 1px 2px rgba(14,42,92,.06),0 2px 6px rgba(14,42,92,.05);
  --shadow-md:0 6px 18px rgba(14,42,92,.09);
  --shadow-lg:0 16px 40px rgba(14,42,92,.14);
  --font-sans:'Pretendard Variable','Pretendard',-apple-system,BlinkMacSystemFont,'Apple SD Gothic Neo','Noto Sans KR','Malgun Gothic',sans-serif;
  --font-serif:'Noto Serif KR',Georgia,'Times New Roman',serif;
  --maxw:1180px;
  --maxw-read:760px;
  --ease:cubic-bezier(.4,0,.2,1);
}
*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{font-family:var(--font-sans);color:var(--ink-900);background:var(--bg);line-height:1.7;font-size:16px;overflow-x:hidden}
img{max-width:100%;height:auto;display:block}
a{color:var(--brand-700);text-decoration:none;transition:color .2s var(--ease)}
a:hover{color:var(--brand-500)}
ul,ol{padding-left:1.35em}
h1,h2,h3,h4{font-weight:800;line-height:1.35;letter-spacing:-.02em;color:var(--ink-900)}
h1{font-size:clamp(1.8rem,4vw,2.6rem)}
h2{font-size:clamp(1.35rem,2.6vw,1.75rem);margin:2.6em 0 .8em}
h3{font-size:clamp(1.1rem,2vw,1.3rem);margin:2em 0 .6em}
p{margin:0 0 1.1em}
:focus-visible{outline:3px solid var(--brand-500);outline-offset:2px;border-radius:4px}
.skip-link{position:absolute;left:-9999px;top:0;background:var(--brand-700);color:#fff;padding:12px 20px;border-radius:0 0 8px 0;z-index:999}
.skip-link:focus{left:0;color:#fff}
/* ============ Site header ============ */
.site-header{position:sticky;top:0;z-index:90;background:rgba(247,250,255,.88);backdrop-filter:blur(14px);-webkit-backdrop-filter:blur(14px);border-bottom:1px solid var(--line)}
.header-inner{max-width:var(--maxw);margin:0 auto;padding:14px 24px;display:flex;align-items:center;gap:20px}
.brand{display:flex;align-items:center;gap:12px;font-weight:800;color:var(--ink-900);font-size:1.06rem;letter-spacing:-.02em}
.brand img{width:38px;height:38px;border-radius:10px;flex:none}
.brand .brand-sub{display:block;font-size:.72rem;font-weight:600;color:var(--ink-500);letter-spacing:-.01em}
.main-nav{display:flex;gap:4px;margin-left:auto;align-items:center}
.main-nav a{display:block;padding:9px 14px;border-radius:10px;font-size:.93rem;font-weight:600;color:var(--ink-700)}
.main-nav a:hover{background:var(--brand-050);color:var(--brand-700)}
.main-nav .cta{background:var(--brand-700);color:#fff;border-radius:10px;padding:10px 18px;margin-left:6px}
.main-nav .cta:hover{background:var(--brand-500);color:#fff}
.nav-toggle{display:none;margin-left:auto;background:none;border:1px solid var(--line);border-radius:10px;width:44px;height:44px;cursor:pointer;align-items:center;justify-content:center;color:var(--ink-900)}
.nav-toggle svg{width:22px;height:22px}
@media(max-width:900px){
  .nav-toggle{display:inline-flex}
  .main-nav{display:none;position:absolute;top:100%;left:0;right:0;background:var(--surface);border-bottom:1px solid var(--line);box-shadow:var(--shadow-md);flex-direction:column;padding:12px 16px 18px;gap:2px;align-items:stretch}
  .main-nav.open{display:flex}
  .main-nav .cta{margin:8px 0 0;text-align:center}
}
/* ============ Layout ============ */
.site-main{min-height:60vh}
.container{max-width:var(--maxw);margin:0 auto;padding:0 24px}
.page-shell{padding:56px 0 96px}
.archive-shell{padding:48px 0 96px}
.single-shell{padding:40px 0 96px}
.entry-content{max-width:var(--maxw-read);margin:0 auto;font-size:1.02rem;line-height:1.8;color:var(--ink-700)}
.entry-content p{margin-bottom:1.25em}
.entry-content a{font-weight:600;text-decoration:underline;text-underline-offset:3px;text-decoration-color:var(--brand-300)}
.entry-content h2{font-family:var(--font-serif);font-weight:800;color:var(--brand-900);border-bottom:2px solid var(--line);padding-bottom:.45em}
.entry-content h2::before{content:"";display:inline-block;width:10px;height:10px;border-radius:3px;background:var(--accent-500);margin-right:10px}
.entry-content h3{color:var(--brand-700)}
.entry-content ul,.entry-content ol{margin:0 0 1.4em;padding-left:1.5em}
.entry-content li{margin-bottom:.45em}
.entry-content img{border-radius:var(--radius-lg);box-shadow:var(--shadow-md);margin:1.6em 0}
/* content tables */
.entry-content table,.kw-table{width:100%;border-collapse:separate;border-spacing:0;border:1px solid var(--line);border-radius:var(--radius-md);overflow:hidden;margin:1.6em 0;font-size:.95rem;display:block;overflow-x:auto;white-space:normal}
.entry-content table thead th,.kw-table thead th{background:var(--brand-700);color:#fff;text-align:left;padding:12px 14px;font-weight:700;white-space:nowrap}
.entry-content table tbody td,.kw-table tbody td{border-top:1px solid var(--line);padding:12px 14px;vertical-align:top}
.entry-content table tbody tr:nth-child(even),.kw-table tbody tr:nth-child(even){background:var(--brand-050)}
.entry-content table tbody tr:hover,.kw-table tbody tr:hover{background:var(--accent-050)}
/* callout */
.entry-content blockquote,.kw-callout{margin:1.8em 0;padding:20px 24px;background:var(--brand-050);border-left:4px solid var(--brand-700);border-radius:0 var(--radius-md) var(--radius-md) 0;color:var(--ink-700);font-size:.98rem}
.entry-content blockquote p,.kw-callout p{margin:0}
/* summary box */
.kw-summary{background:linear-gradient(135deg,var(--brand-050),var(--accent-050));border:1px solid var(--line);border-radius:var(--radius-lg);padding:22px 26px;margin:0 0 2.2em}
.kw-summary>strong{display:block;font-size:.85rem;letter-spacing:.06em;color:var(--brand-700);margin-bottom:10px;text-transform:uppercase}
.kw-summary ul{margin:0;padding-left:1.2em}
.kw-summary li{margin-bottom:.4em}
/* flow diagram */
.kw-flow{display:flex;flex-wrap:wrap;align-items:stretch;gap:10px;margin:1.8em 0}
.kw-flow-step{flex:1 1 140px;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius-md);padding:16px 14px;text-align:center;box-shadow:var(--shadow-sm)}
.kw-flow-step b{display:block;font-size:.95rem;color:var(--brand-700);margin-bottom:4px}
.kw-flow-step span{display:block;font-size:.8rem;color:var(--ink-500)}
.kw-flow-arrow{align-self:center;font-size:1.3rem;color:var(--accent-500);font-weight:800;flex:none}

/* figure */
.kw-figure{margin:1.8em 0}
.kw-figure img{border-radius:var(--radius-lg);box-shadow:var(--shadow-md)}
.kw-figure figcaption{font-size:.8rem;color:var(--ink-400);text-align:center;margin-top:8px}

/* notice boxes */
.legal-notice,.ai-notice{max-width:var(--maxw-read);margin-left:auto;margin-right:auto}
/* ============ Post meta & header ============ */
.post-header{max-width:var(--maxw-read);margin:0 auto 2.2em}
.post-cat{display:inline-block;background:var(--brand-050);color:var(--brand-700);border:1px solid var(--brand-100);padding:5px 12px;border-radius:999px;font-size:.8rem;font-weight:700;margin-bottom:16px}
.post-title{font-family:var(--font-serif);font-weight:800;color:var(--brand-900);line-height:1.28;margin-bottom:14px;letter-spacing:-.02em}
.post-meta{display:flex;flex-wrap:wrap;gap:8px 18px;color:var(--ink-400);font-size:.86rem}
.post-meta .sep{color:var(--line)}
.featured-image{border-radius:var(--radius-xl);overflow:hidden;box-shadow:var(--shadow-lg);margin:0 auto 2.4em;max-width:var(--maxw-read)}
.featured-image img{width:100%;object-fit:cover;aspect-ratio:16/9}
/* ============ Cards / grids ============ */
.post-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:24px;margin-top:28px}
.post-card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius-lg);overflow:hidden;box-shadow:var(--shadow-sm);transition:transform .22s var(--ease),box-shadow .22s var(--ease);display:flex;flex-direction:column}
.post-card:hover{transform:translateY(-4px);box-shadow:var(--shadow-md)}
.post-card .thumb{aspect-ratio:16/9;overflow:hidden;background:var(--surface-soft)}
.post-card .thumb img{width:100%;height:100%;object-fit:cover;transition:transform .4s var(--ease)}
.post-card:hover .thumb img{transform:scale(1.045)}
.post-card .card-body{padding:20px 22px 22px;display:flex;flex-direction:column;flex:1;gap:8px}
.post-card .card-cat{font-size:.74rem;font-weight:700;color:var(--accent-600);letter-spacing:.03em}
.post-card h3{font-size:1.08rem;font-weight:800;line-height:1.45;margin:0}
.post-card h3 a{color:var(--ink-900)}
.post-card h3 a:hover{color:var(--brand-700)}
.post-card .card-excerpt{font-size:.88rem;color:var(--ink-500);line-height:1.65;display:-webkit-box;-webkit-line-clamp:3;-webkit-box-orient:vertical;overflow:hidden}
.post-card .card-meta{margin-top:auto;padding-top:10px;font-size:.78rem;color:var(--ink-400);border-top:1px dashed var(--line)}
@media(max-width:980px){.post-grid{grid-template-columns:repeat(2,1fr)}}
@media(max-width:620px){.post-grid{grid-template-columns:1fr}}
/* ============ Related / archive head ============ */
.archive-head{margin-bottom:12px}
.archive-head h1{font-family:var(--font-serif);color:var(--brand-900)}
.archive-head .archive-desc{color:var(--ink-500);max-width:640px;margin-top:8px}
.section-title{font-family:var(--font-serif);font-size:clamp(1.4rem,2.6vw,1.8rem);font-weight:800;color:var(--brand-900);margin-bottom:8px}
.section-sub{color:var(--ink-500);max-width:640px;margin-bottom:24px}
/* ============ Prev/next ============ */
.post-nav{max-width:var(--maxw-read);margin:3.2em auto 0;display:grid;grid-template-columns:1fr 1fr;gap:16px}
.post-nav a{display:block;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius-md);padding:16px 18px;font-size:.88rem;color:var(--ink-700);box-shadow:var(--shadow-sm);transition:border-color .2s,transform .2s}
.post-nav a:hover{border-color:var(--brand-300);transform:translateY(-2px);color:var(--brand-700)}
.post-nav .nav-label{display:block;font-size:.72rem;font-weight:700;color:var(--ink-400);margin-bottom:4px;letter-spacing:.05em}
@media(max-width:620px){.post-nav{grid-template-columns:1fr}}
/* ============ Pagination ============ */
.pagination{display:flex;gap:8px;justify-content:center;margin-top:44px}
.pagination .page-numbers{padding:9px 15px;border-radius:10px;background:var(--surface);border:1px solid var(--line);color:var(--ink-700);font-weight:600;min-width:44px;text-align:center}
.pagination .page-numbers.current{background:var(--brand-700);color:#fff;border-color:var(--brand-700)}
.pagination a:hover{border-color:var(--brand-300);color:var(--brand-700)}
/* ============ 404 / page ============ */
.notfound{text-align:center;padding:90px 20px}
.notfound .nf-code{font-family:var(--font-serif);font-size:clamp(3rem,8vw,5rem);font-weight:800;color:var(--brand-100);line-height:1}
.notfound h1{font-size:1.5rem;margin:16px 0 10px}
.notfound p{color:var(--ink-500)}
/* ============ Footer ============ */
.site-footer{background:var(--brand-900);color:#C8D3E2;margin-top:80px}
.footer-inner{max-width:var(--maxw);margin:0 auto;padding:64px 24px 36px}
.footer-grid{display:grid;grid-template-columns:1.6fr 1fr 1fr;gap:40px;margin-bottom:40px}
.footer-brand{font-size:1.1rem;font-weight:800;color:#fff;margin-bottom:12px}
.footer-brand img{width:34px;height:34px;border-radius:9px;display:inline-block;vertical-align:-8px;margin-right:10px}
.footer-desc{font-size:.88rem;color:#93A5C4;max-width:340px;line-height:1.7}
.footer-col h4{color:#fff;font-size:.85rem;letter-spacing:.06em;margin-bottom:14px}
.footer-col ul{list-style:none;padding:0}
.footer-col li{margin-bottom:9px}
.footer-col a{color:#C8D3E2;font-size:.9rem}
.footer-col a:hover{color:#fff}
.footer-notices{border-top:1px solid rgba(255,255,255,.12);padding-top:28px;margin-top:8px}
.footer-notices p{font-size:.8rem;color:#93A5C4;line-height:1.75;margin-bottom:8px}
.footer-bottom{margin-top:26px;display:flex;flex-wrap:wrap;gap:10px 24px;align-items:center;justify-content:space-between;font-size:.78rem;color:#7C8BA0}
.footer-bottom a{color:#93A5C4}
.footer-bottom a:hover{color:#fff}
@media(max-width:820px){.footer-grid{grid-template-columns:1fr;gap:28px}}
/* ============ Comments (비노출) ============ */
#comments,.comments-area{display:none}
/* ============ Reduced motion ============ */
@media(prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important}
}