:root{
  --bg-deep:#0a0d14;
  --bg-surface:#101521;
  --bg-elev:#141a28;
  --line:rgba(255,255,255,0.08);
  --line-strong:rgba(255,255,255,0.16);
  --text-primary:#e8ecf4;
  --text-secondary:#a4adc0;
  --text-muted:#6b7387;
  --accent:#4f7df5;
  --accent-2:#22d3a7;
  --accent-violet:#a78bfa;
  --accent-amber:#f0b341;
  --radius-sm:8px;
  --radius-md:14px;
  --radius-lg:22px;
  --ease:cubic-bezier(.2,.7,.2,1);
}

*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  font-family:'Inter',system-ui,sans-serif;
  background:var(--bg-deep);
  color:var(--text-primary);
  -webkit-font-smoothing:antialiased;
  min-height:100vh;
}

/* SECTION */
.linkup-development-approach{
  position:relative;
  padding:clamp(64px,9vw,140px) clamp(20px,5vw,72px);
  background:
    radial-gradient(1100px 600px at 90% -10%, rgba(79,125,245,.10), transparent 60%),
    radial-gradient(900px 500px at -10% 110%, rgba(34,211,167,.08), transparent 60%),
    var(--bg-deep);
  overflow:hidden;
}
.linkup-development-approach::before{
  content:"";
  position:absolute;inset:0;
  background-image:
    linear-gradient(var(--line) 1px,transparent 1px),
    linear-gradient(90deg,var(--line) 1px,transparent 1px);
  background-size:64px 64px;
  mask-image:radial-gradient(ellipse at 50% 30%, #000 30%, transparent 75%);
  opacity:.35;
  pointer-events:none;
}
.development-approach-container{
  position:relative;
  max-width:1240px;
  margin:0 auto;
}

/* HEADER */
.section-header{
  display:flex;flex-direction:column;gap:14px;
  margin-bottom:clamp(36px,5vw,64px);
  max-width:760px;
}
.da-eyebrow{
  display:inline-flex;align-items:center;gap:8px;
  font-family:'JetBrains Mono',monospace;
  font-size:11px;letter-spacing:.18em;text-transform:uppercase;
  color:var(--text-secondary);
  padding:6px 12px;border:1px solid var(--line);border-radius:999px;
  width:fit-content;
  background:rgba(255,255,255,.02);
}
.da-dot{
  width:6px;height:6px;border-radius:50%;
  background:var(--accent-2);
  box-shadow:0 0 0 4px rgba(34,211,167,.18);
}
.section-title{
  font-size:clamp(34px,5.4vw,60px);
  line-height:1.02;letter-spacing:-.025em;
  font-weight:600;margin:0;
  background:linear-gradient(180deg,#fff 0%,#cdd5e6 100%);
  -webkit-background-clip:text;background-clip:text;color:transparent;
}
.da-lede{
  margin:0;color:var(--text-secondary);
  font-size:clamp(15px,1.5vw,17px);line-height:1.55;
  max-width:560px;
}

/* LAYOUT */
.development-approach-content{
  display:grid;
  grid-template-columns:240px 1fr;
  gap:clamp(28px,4vw,56px);
  align-items:start;
}

/* RAIL */
.da-rail{
  position:sticky;top:24px;
  display:flex;flex-direction:column;gap:18px;
}
.da-rail-list{
  list-style:none;margin:0;padding:0;
  display:flex;flex-direction:column;gap:4px;
}
.da-rail-btn{
  width:100%;
  display:flex;align-items:center;gap:14px;
  padding:14px 16px;
  background:transparent;
  border:1px solid transparent;
  border-radius:var(--radius-md);
  color:var(--text-muted);
  font:500 14px/1 'Inter',sans-serif;
  cursor:pointer;text-align:left;
  transition:all .3s var(--ease);
}
.da-rail-btn:hover{color:var(--text-primary);background:rgba(255,255,255,.025)}
.da-rail-btn.is-active{
  color:var(--text-primary);
  background:linear-gradient(180deg,rgba(79,125,245,.10),rgba(79,125,245,.02));
  border-color:var(--line-strong);
}
.da-rail-num{
  font-family:'JetBrains Mono',monospace;
  font-size:11px;color:var(--text-muted);
  width:22px;
}
.da-rail-btn.is-active .da-rail-num{color:var(--accent)}
.da-rail-label{font-size:14px;letter-spacing:-.005em}
.da-rail-progress{
  position:relative;height:2px;border-radius:2px;
  background:var(--line);overflow:hidden;
}
.da-rail-fill{
  position:absolute;inset:0;width:25%;
  background:linear-gradient(90deg,var(--accent),var(--accent-2));
  transition:width .5s var(--ease);
  border-radius:2px;
}

/* PANELS */
.da-panels{
  display:flex;flex-direction:column;gap:clamp(18px,2.5vw,28px);
}
.da-panel{
  position:relative;
  padding:clamp(26px,3vw,40px);
  border:1px solid var(--line);
  border-radius:var(--radius-lg);
  background:
    linear-gradient(180deg, rgba(255,255,255,.02), rgba(255,255,255,0)),
    var(--bg-surface);
  overflow:hidden;
  opacity:0;transform:translateY(28px);
  transition:opacity .7s var(--ease),transform .7s var(--ease),border-color .3s ease;
}
.da-panel.is-in{opacity:1;transform:none}
.da-panel:hover{border-color:var(--line-strong)}

.da-panel::before{
  content:"";
  position:absolute;left:0;top:0;bottom:0;width:3px;
  background:var(--accent);
  opacity:.7;
}
.da-panel[data-accent="teal"]::before{background:var(--accent-2)}
.da-panel[data-accent="violet"]::before{background:var(--accent-violet)}
.da-panel[data-accent="amber"]::before{background:var(--accent-amber)}

.da-panel::after{
  content:"";
  position:absolute;inset:0;
  background:radial-gradient(420px circle at var(--mx,80%) var(--my,0%), rgba(79,125,245,.10), transparent 60%);
  opacity:0;transition:opacity .35s ease;
  pointer-events:none;
}
.da-panel[data-accent="teal"]::after{background:radial-gradient(420px circle at var(--mx,80%) var(--my,0%), rgba(34,211,167,.10), transparent 60%)}
.da-panel[data-accent="violet"]::after{background:radial-gradient(420px circle at var(--mx,80%) var(--my,0%), rgba(167,139,250,.10), transparent 60%)}
.da-panel[data-accent="amber"]::after{background:radial-gradient(420px circle at var(--mx,80%) var(--my,0%), rgba(240,179,65,.10), transparent 60%)}
.da-panel:hover::after{opacity:1}

.da-panel-head{
  display:flex;align-items:center;justify-content:space-between;
  margin-bottom:18px;
}
.da-index{
  font-family:'JetBrains Mono',monospace;
  font-size:11px;letter-spacing:.18em;text-transform:uppercase;
  color:var(--text-muted);
}
.da-tag{
  font-family:'JetBrains Mono',monospace;
  font-size:10.5px;letter-spacing:.14em;text-transform:uppercase;
  padding:5px 10px;border-radius:999px;
  border:1px solid var(--line-strong);
  color:var(--text-secondary);
  background:rgba(255,255,255,.02);
}

.da-panel-title{
  margin:0 0 14px;
  font-size:clamp(20px,2.4vw,26px);
  line-height:1.25;letter-spacing:-.015em;
  font-weight:600;color:var(--text-primary);
  max-width:38ch;
}
.development-approach-text{
  margin:0;
  font-size:clamp(14.5px,1.4vw,16px);
  line-height:1.65;color:var(--text-secondary);
  max-width:62ch;
}

.da-meta{
  display:flex;align-items:center;justify-content:space-between;
  flex-wrap:wrap;gap:12px;
  margin-top:22px;padding-top:18px;
  border-top:1px dashed var(--line);
  font-family:'JetBrains Mono',monospace;
  font-size:12px;color:var(--text-muted);
}
.da-meta b{color:var(--text-secondary);font-weight:500}
.da-mono{color:var(--text-muted)}

/* GLYPH */
.da-glyph{
  position:absolute;
  right:-30px;bottom:-30px;
  width:180px;height:180px;
  opacity:.10;
  pointer-events:none;
  transition:opacity .35s ease,transform .6s var(--ease);
}
.da-panel:hover .da-glyph{opacity:.18;transform:rotate(8deg) scale(1.05)}
.da-glyph svg{width:100%;height:100%;fill:none;stroke:var(--accent);stroke-width:1.5}
.da-panel[data-accent="teal"] .da-glyph svg{stroke:var(--accent-2)}
.da-panel[data-accent="violet"] .da-glyph svg{stroke:var(--accent-violet)}
.da-panel[data-accent="amber"] .da-glyph svg{stroke:var(--accent-amber)}

/* RESPONSIVE */
@media (max-width:880px){
  .development-approach-content{grid-template-columns:1fr;gap:24px}
  .da-rail{position:static}
  .da-rail-list{flex-direction:row;overflow-x:auto;gap:8px;scrollbar-width:none}
  .da-rail-list::-webkit-scrollbar{display:none}
  .da-rail-btn{white-space:nowrap;padding:10px 14px}
  .da-rail-progress{display:none}
  .da-glyph{width:130px;height:130px;opacity:.07}
}
@media (max-width:520px){
  .da-panel-head{flex-direction:column;align-items:flex-start;gap:8px}
  .da-meta{font-size:11px}
}

@media (prefers-reduced-motion: reduce){
  .da-panel{opacity:1;transform:none;transition:none}
  .da-rail-fill{transition:none}
  .da-glyph{transition:none}
}