:root{
  --bg:#0b0c10;
  --card:#11131a;
  --text:#e8e8ee;
  --muted:#a8acb8;
  --line:#222635;
  --accent:#f5c542;
}

*{box-sizing:border-box;}
body{
  margin:0;
  font-family:system-ui,-apple-system,Segoe UI,Roboto,Arial,sans-serif;
  background:var(--bg);
  color:var(--text);
}

/* Sticky summary */
.summaryBar{
  position:sticky;
  top:0;
  z-index:20;
  backdrop-filter: blur(10px);
  background: rgba(10,12,16,.72);
  border-bottom:1px solid rgba(255,255,255,.08);
}
.summaryInner{
  max-width: 1200px;
  margin: 0 auto;
  padding: 14px 18px;
  display:grid;
  grid-template-columns: 1.2fr 1fr auto;
  gap: 14px;
  align-items:center;
}
.h1{font-size:20px; font-weight:700; margin-bottom:4px;}
.sub{font-size:12px; color:var(--muted);}

.summaryCards{
  display:grid;
  grid-template-columns: repeat(3, minmax(0,1fr));
  gap:10px;
}
.sumCard{
  border:1px solid rgba(255,255,255,.10);
  background: rgba(17,19,26,.55);
  border-radius:14px;
  padding:10px 12px;
}
.sumCard.accent{
  border-color: rgba(245,197,66,.45);
}
.sumLabel{font-size:11px; color:var(--muted); text-transform:uppercase; letter-spacing:.07em;}
.sumValue{font-size:16px; font-weight:700; margin-top:4px; font-variant-numeric: tabular-nums;}

.summaryActions{
  display:flex;
  gap:10px;
  justify-content:flex-end;
  flex-wrap:wrap;
}

/* Layout */
.container{max-width:1200px; margin:0 auto; padding:18px;}
.grid{
  display:grid;
  grid-template-columns: 1fr;
  gap: 14px;
}
@media (min-width: 980px){
  .grid{grid-template-columns: 1fr 1fr;}
}

/* Cards */
.card{
  background:var(--card);
  border:1px solid var(--line);
  border-radius:16px;
  padding:14px;
  box-shadow: 0 10px 30px rgba(0,0,0,.25);
}
.cardHead{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap:12px;
  margin-bottom:10px;
}
.cardHead h2{margin:0; font-size:18px;}

/* Collapsible panels */
.panel{
  border:1px solid rgba(255,255,255,.08);
  border-radius:14px;
  background:#0f1118;
  margin-bottom:10px;
  overflow:hidden;
}
.panel summary{
  cursor:pointer;
  padding:10px 12px;
  color: var(--text);
  font-weight:600;
  user-select:none;
  list-style:none;
}
.panel summary::-webkit-details-marker{display:none;}
.panel summary::after{
  content:"▾";
  float:right;
  opacity:.7;
}
.panel[open] summary::after{content:"▴";}
.panel .form{
  padding: 10px 12px 12px;
  display:grid;
  gap:10px;
}

/* Inputs */
.row{
  display:grid;
  grid-template-columns: 1fr 170px;
  gap: 10px;
  align-items:center;
}
label{font-size:13px;}
input{
  width:100%;
  padding:9px 10px;
  border-radius:12px;
  border:1px solid rgba(255,255,255,.10);
  background:#0b0d13;
  color:var(--text);
  outline:none;
}
input:focus{border-color: rgba(245,197,66,.55);}

.inputWrap{position:relative;}
.inputWrap input{padding-right:34px;}
.suffix{
  position:absolute;
  right:10px;
  top:50%;
  transform:translateY(-50%);
  font-size:12px;
  opacity:.6;
  pointer-events:none;
}

.sectionTitle{
  margin: 14px 0 8px;
  font-size:12px;
  letter-spacing:.08em;
  text-transform:uppercase;
  color:var(--muted);
}

/* Outputs */
.outputs{display:grid; gap:8px;}
.outRow{
  display:flex;
  justify-content:space-between;
  gap:12px;
  padding:9px 10px;
  border:1px solid rgba(255,255,255,.10);
  border-radius:12px;
  background:#0f1118;
}
.outRow span{color:var(--muted); font-size:13px;}
.outRow strong{font-variant-numeric: tabular-nums;}

.divider{
  height:1px;
  background: rgba(255,255,255,.08);
  margin: 8px 0;
}

/* Buttons */
.btn{
  appearance:none;
  border:1px solid rgba(255,255,255,.14);
  background:#0f1118;
  color:var(--text);
  padding:8px 10px;
  border-radius:12px;
  cursor:pointer;
}
.btn:hover{border-color: rgba(245,197,66,.45);}
.btn.primary{
  border-color: rgba(245,197,66,.55);
}

@media (max-width: 980px){
  .summaryInner{
    grid-template-columns: 1fr;
  }
  .summaryActions{
    justify-content:flex-start;
  }
}
.card.winner {
  border-color: rgba(80,200,120,.8);
  box-shadow: 0 0 0 1px rgba(80,200,120,.6),
              0 10px 40px rgba(80,200,120,.15);
}
<div class="outRow">
  <span>Damage Gain %</span>
  <strong id="b2_out_damageGainPct">—</strong>
</div>