/* ============================================================
   Keyword Clustering Tool — premium light system (indigo / hue 274)
   Shared by /tools/keyword-cluster/ and its pSEO subpages.
   Class vocabulary preserved; only the visual system is new.
   ============================================================ */
:root{
  --ink:oklch(24% .02 264);--muted:oklch(52% .03 264);--paper:oklch(97% .008 264);
  --surface:oklch(100% .002 264);--line:oklch(90% .015 264);
  --accent:oklch(56% .19 274);--accent-dark:oklch(46% .17 274);--accent-soft:oklch(94% .04 274);
  --success:oklch(56% .13 155);--success-soft:oklch(94% .05 155);

  /* Compatibility aliases: legacy var names used by subpage inline styles + app.js */
  --text:var(--ink);--text-main:var(--ink);--heading:var(--ink);--primary:var(--ink);
  --primary-hover:var(--accent-dark);--text-muted:var(--muted);--bg:var(--paper);
  --bg-main:var(--paper);--header-bg:var(--surface);--section-alt-bg:var(--paper);
  --card-bg:var(--surface);--panel-bg:var(--paper);--border:var(--line);
  --accent-hover:var(--accent-dark);--radius:14px;

  font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;
  color:var(--ink);font-synthesis:none;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{background:var(--paper);font-size:16px;line-height:1.55;overflow-x:hidden}
button,input,textarea{font:inherit}
button{cursor:pointer}
a{color:inherit}

/* ---------- Header ---------- */
.site-header{min-height:74px;display:flex;align-items:center;gap:32px;padding:0 clamp(16px,5vw,72px);border-bottom:1px solid var(--line);background:var(--surface);position:sticky;top:0;z-index:20}
.logo,.brand{font-size:18px;font-weight:850;letter-spacing:-.04em;text-decoration:none;color:var(--ink)}
.logo span,.brand span{color:var(--accent)}
.site-header nav{display:flex;gap:24px;margin-left:auto;font-size:14px;color:var(--muted)}
.site-header nav a{text-decoration:none;transition:color .18s}
.site-header nav a:hover{color:var(--accent-dark)}
.menu-btn{display:none;margin-left:auto;border:1px solid var(--line);background:var(--surface);padding:9px 14px;border-radius:9px;color:var(--ink);font-weight:700}

/* ---------- Hero ---------- */
.page-wrapper{max-width:1200px;margin:auto;padding:0 clamp(16px,5vw,72px) 40px}
.hero{padding:64px 0 40px;max-width:860px}
.section-kicker{display:block;text-transform:uppercase;letter-spacing:.11em;font-size:11px;font-weight:850;color:var(--accent-dark)}
.hero-badge{display:inline-flex;align-items:center;gap:8px;text-transform:uppercase;letter-spacing:.1em;font-size:11px;font-weight:850;color:var(--accent-dark);background:var(--accent-soft);padding:7px 14px;border-radius:999px}
.page-title{font-size:clamp(40px,6.5vw,76px);line-height:1;letter-spacing:-.055em;margin:18px 0 18px;text-wrap:balance}
.page-title em{font-style:normal;color:var(--accent)}
.page-subtitle{max-width:680px;color:var(--muted);font-size:18px;line-height:1.6}
.hero-note{display:inline-flex;align-items:center;gap:9px;margin-top:22px;color:var(--muted);font-size:13px}
.status-dot{width:8px;height:8px;border-radius:50%;background:var(--accent);box-shadow:0 0 0 5px var(--accent-soft)}

/* ---------- App layout ---------- */
.app-layout{display:grid;grid-template-columns:380px minmax(0,1fr);gap:24px;align-items:start;margin-bottom:24px}
.input-panel,.output-panel{background:var(--surface);border:1px solid var(--line);border-radius:18px;box-shadow:0 18px 40px oklch(24% .04 264 / .06)}
.input-panel{display:flex;flex-direction:column;gap:20px;padding:24px;position:sticky;top:94px}
.output-panel{min-height:600px;display:flex;flex-direction:column;overflow:hidden}
.panel-header{display:flex;align-items:baseline;justify-content:space-between;gap:12px}
.panel-header h2{font-size:16px;font-weight:800;letter-spacing:-.02em}
.hint{font-size:13px;color:var(--muted);line-height:1.5}

/* Textarea */
.textarea-wrapper{position:relative}
#keyword-input{width:100%;height:360px;padding:16px;border:1px solid var(--line);border-radius:12px;background:var(--paper);color:var(--ink);font-family:ui-monospace,"SF Mono",Menlo,Consolas,monospace;font-size:14px;line-height:1.6;resize:none;outline:none;transition:border-color .18s,box-shadow .18s}
#keyword-input:focus{border-color:var(--accent);box-shadow:0 0 0 4px var(--accent-soft)}
.stats-bar{display:flex;justify-content:space-between;align-items:center;margin-top:10px;font-size:13px;color:var(--muted);font-weight:600}
.btn-text{background:transparent;border:none;color:var(--accent-dark);font-weight:750;padding:6px 4px;min-height:36px;border-radius:8px;transition:color .18s}
.btn-text:hover{color:var(--accent);text-decoration:underline}
.stats-actions{display:inline-flex;align-items:center;gap:4px}

/* Settings */
.settings-panel{background:var(--paper);border:1px solid var(--line);border-radius:13px;padding:16px}
.settings-panel h3{font-size:12px;text-transform:uppercase;letter-spacing:.08em;color:var(--muted);font-weight:850;margin-bottom:14px}
.slider-group{display:flex;align-items:center;gap:14px;margin-bottom:10px}
input[type=range]{flex:1;width:100%;accent-color:var(--accent)}
#threshold-value{font-size:13px;font-weight:750;min-width:96px;text-align:right;color:var(--ink);font-variant-numeric:tabular-nums}

/* Buttons */
.btn-primary,.btn-secondary,.btn-action{min-height:44px;border-radius:11px;font-weight:750;transition:transform .18s cubic-bezier(.16,1,.3,1),background .18s,border-color .18s,box-shadow .18s}
.btn-primary{display:flex;align-items:center;justify-content:center;gap:9px;background:var(--accent);color:oklch(99% .01 274);border:1px solid var(--accent);padding:14px 24px;font-size:16px;box-shadow:0 10px 24px oklch(56% .19 274 / .28)}
.btn-primary:hover{transform:translateY(-2px);background:var(--accent-dark);border-color:var(--accent-dark)}
.full-width-btn{width:100%}
.header-actions{padding:22px 24px;border-bottom:1px solid var(--line)}
.action-buttons{display:flex;gap:10px}
.btn-secondary{background:var(--surface);color:var(--ink);border:1px solid var(--line);padding:9px 16px;font-size:13px}
.btn-secondary:hover:not(:disabled){transform:translateY(-1px);border-color:var(--accent);background:var(--accent-soft)}
.btn-action{background:var(--accent);color:oklch(99% .01 274);border:1px solid var(--accent);padding:9px 16px;font-size:13px}
.btn-action:hover:not(:disabled){transform:translateY(-1px);background:var(--accent-dark);border-color:var(--accent-dark)}
button:disabled{opacity:.5;cursor:not-allowed}
.btn-primary[aria-busy=true]{opacity:.85}
.btn-secondary.is-copied,.btn-action.is-copied{background:var(--success-soft);border-color:var(--success);color:var(--success)}

/* Results */
.results-container{padding:24px;flex:1;background:var(--paper)}
.empty-state{display:flex;flex-direction:column;align-items:center;justify-content:center;height:100%;min-height:360px;color:var(--muted);text-align:center;gap:16px;padding:40px}
.empty-state svg{color:var(--line)}
.empty-state p{max-width:34ch}

/* Clusters (rendered by app.js) */
.result-summary{font-size:13px;color:var(--muted);margin-bottom:16px}
.result-summary strong{color:var(--ink);font-weight:800}
.cluster-role{display:block;font-weight:400;font-size:12px;color:var(--muted);margin-top:2px}
.cluster-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:18px}
.cluster-card{background:var(--surface);border:1px solid var(--line);border-radius:14px;overflow:hidden;box-shadow:0 1px 2px oklch(24% .04 264 / .05);transition:transform .18s cubic-bezier(.16,1,.3,1),box-shadow .18s,border-color .18s}
.cluster-card:hover{transform:translateY(-2px);border-color:var(--accent);box-shadow:0 12px 26px var(--accent-soft)}
.cluster-header{background:var(--paper);padding:14px 16px;border-bottom:1px solid var(--line);display:flex;justify-content:space-between;align-items:flex-start;gap:10px}
.cluster-title{font-size:15px;font-weight:800;color:var(--ink);line-height:1.3;letter-spacing:-.01em}
.cluster-badge{flex:none;background:var(--accent-soft);color:var(--accent-dark);padding:4px 10px;border-radius:999px;font-size:12px;font-weight:800;font-variant-numeric:tabular-nums}
.cluster-body{padding:8px 16px;max-height:250px;overflow-y:auto}
.keyword-item{font-size:13px;color:var(--ink);padding:8px 0;border-bottom:1px dashed var(--line)}
.keyword-item:last-child{border-bottom:none}
.keyword-vol{color:var(--muted);font-size:11px;margin-left:8px}

/* ---------- SEO content ---------- */
.seo-content{max-width:960px;margin:0 auto;padding:72px 0 24px;border-top:1px solid var(--line)}
.seo-content h2{font-size:clamp(28px,4vw,44px);line-height:1.05;letter-spacing:-.055em;margin:44px 0 16px;text-wrap:balance}
.seo-content .section-kicker+h2{margin-top:10px}
.seo-content p{color:var(--muted);line-height:1.75;margin-bottom:14px;max-width:72ch}
.seo-content strong{color:var(--ink)}
.how-to-steps{max-width:72ch;margin:8px 0 14px;padding-left:22px;color:var(--muted);line-height:1.75}
.how-to-steps li{margin-bottom:10px}
.how-to-steps strong{color:var(--ink)}

/* Cluster diagram */
.cluster-diagram{background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:40px;margin:28px 0;display:flex;flex-direction:column;align-items:center;gap:32px}
.diagram-core{background:var(--ink);color:var(--surface);padding:22px 36px;border-radius:14px;text-align:center;line-height:1.5;box-shadow:0 14px 30px oklch(24% .04 264 / .18);position:relative;z-index:2}
.diagram-core em,.spoke em{color:var(--accent-soft);font-style:normal}
.diagram-spokes{display:flex;gap:24px;justify-content:center;position:relative;flex-wrap:wrap}
.diagram-spokes::before{content:'';position:absolute;top:-32px;left:50%;width:2px;height:32px;background:var(--line)}
.diagram-spokes::after{content:'';position:absolute;top:-20px;left:17%;right:17%;height:2px;background:var(--line)}
.spoke{background:var(--surface);border:2px solid var(--accent);color:var(--ink);padding:16px 22px;border-radius:12px;text-align:center;font-size:14px;line-height:1.5;position:relative}
.spoke em{color:var(--accent-dark)}
.spoke::before{content:'';position:absolute;top:-20px;left:50%;width:2px;height:20px;background:var(--line)}

/* Reasons */
.reasons-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px;margin-top:36px}
.reason-card{background:var(--surface);border:1px solid var(--line);border-radius:16px;padding:24px;transition:transform .18s cubic-bezier(.16,1,.3,1),border-color .18s,box-shadow .18s}
.reason-card:hover{transform:translateY(-2px);border-color:var(--accent);box-shadow:0 12px 26px var(--accent-soft)}
.reason-card h3{font-size:17px;letter-spacing:-.02em;margin-bottom:10px;color:var(--accent-dark)}
.reason-card p{font-size:14px;color:var(--muted);line-height:1.7}

/* ---------- FAQ + Related ---------- */
.dt-container{max-width:1200px;margin:0 auto;padding:0 clamp(16px,5vw,72px)}
.dt-mb-16{margin-bottom:72px}
.faq-section{max-width:820px;margin:0 auto;padding:16px clamp(16px,5vw,72px) 0}
.faq-heading,.related-heading{font-size:clamp(24px,3.2vw,34px);letter-spacing:-.05em;margin-bottom:20px;text-wrap:balance}
.faq-list{display:flex;flex-direction:column}
.faq-item{border-top:1px solid var(--line)}
.faq-item summary{cursor:pointer;font-weight:800;letter-spacing:-.01em;list-style:none;display:flex;justify-content:space-between;align-items:center;gap:18px;padding:18px 0;min-height:44px}
.faq-item summary::-webkit-details-marker{display:none}
.faq-item summary::after{content:'+';color:var(--accent-dark);font-size:22px;font-weight:400;line-height:1}
.faq-item[open] summary::after{content:'\2212'}
.faq-item p{color:var(--muted);line-height:1.7;font-size:15px;padding:0 0 18px}

.related-section{max-width:1200px;margin:0 auto;padding:8px clamp(16px,5vw,72px) 0}
.related-heading{font-size:13px;text-transform:uppercase;letter-spacing:.09em;color:var(--muted);margin-bottom:16px}
.related-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:12px}
.related-card{display:flex;align-items:center;padding:16px 18px;border:1px solid var(--line);border-radius:13px;background:var(--surface);text-decoration:none;font-weight:750;font-size:14px;color:var(--ink);transition:transform .18s cubic-bezier(.16,1,.3,1),border-color .18s,color .18s}
.related-card:hover{transform:translateY(-2px);border-color:var(--accent);color:var(--accent-dark)}

.site-footer{margin-top:24px;padding:28px clamp(16px,5vw,72px);border-top:1px solid var(--line);color:var(--muted);font-size:13px;text-align:center}
.site-footer a{color:var(--accent-dark);text-decoration:none}
.site-footer a:hover{text-decoration:underline}

/* ---------- Focus + motion ---------- */
:focus-visible{outline:3px solid var(--accent);outline-offset:3px;border-radius:4px}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{scroll-behavior:auto!important;transition-duration:.01ms!important;animation-duration:.01ms!important}}

/* ---------- Responsive ---------- */
@media(max-width:900px){
  .app-layout{grid-template-columns:1fr}
  .input-panel{position:static}
  #keyword-input{height:220px}
  .reasons-grid{grid-template-columns:1fr}
  .diagram-spokes{flex-direction:column;align-items:center}
  .diagram-spokes::before,.diagram-spokes::after,.spoke::before{display:none}
}
@media(max-width:640px){
  .site-header{min-height:62px;gap:16px}
  .site-header nav{display:none;position:absolute;top:62px;left:0;right:0;flex-direction:column;gap:4px;padding:12px clamp(16px,5vw,72px);background:var(--surface);border-bottom:1px solid var(--line);z-index:30}
  .site-header nav.open{display:flex}
  .site-header nav a{padding:12px 4px;font-size:16px;font-weight:700;min-height:44px;display:flex;align-items:center}
  .menu-btn{display:block}
  .hero{padding:44px 0 28px}
  .page-title{font-size:clamp(36px,11vw,60px)}
  .input-panel,.results-container{padding:18px}
  .header-actions{padding:16px 18px}
  .cluster-diagram{padding:24px}
  .seo-content{padding-top:56px}
}

/* ---------- Scrollbar (light / indigo) ---------- */
*{scrollbar-width:thin;scrollbar-color:oklch(56% .19 274 / .4) oklch(97% .008 264)}
::-webkit-scrollbar{width:8px;height:8px}
::-webkit-scrollbar-track{background:transparent}
::-webkit-scrollbar-thumb{background:oklch(56% .19 274 / .35);border-radius:10px}
::-webkit-scrollbar-thumb:hover{background:oklch(56% .19 274 / .6)}