:root{
  --bg:#030b13;
  --grid:#0ff1;
  --neon:#00e5ff;
  --neon2:#7c4dff;
  --text:#d8f6ff;
}

html,body{height:100%}
body{
  margin:0;
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background:
    radial-gradient(1200px 700px at 20% 10%, #0b1b2a 0%, transparent 60%),
    radial-gradient(900px 600px at 90% 80%, #1a0b2a 0%, transparent 55%),
    linear-gradient(180deg, var(--bg), #02060a);
  color:var(--text);
  display:flex;
  align-items:center;
  justify-content:center;
}

.shell{
  width:min(520px, calc(100vw - 32px));
}

.topbar{
  display:flex;
  align-items:center;
  justify-content:space-between;
  margin-bottom:14px;
}
.topbar a{
  color:var(--neon);
  text-decoration:none;
  border:1px solid #00e5ff44;
  padding:8px 10px;
  border-radius:10px;
  box-shadow:0 0 18px #00e5ff22 inset;
}
.topbar h1{
  margin:0;
  font-size:18px;
  letter-spacing:0.08em;
  text-transform:uppercase;
  color:#e9fdff;
}

.frame{
  border:1px solid #00e5ff55;
  border-radius:18px;
  padding:16px;
  background:
    linear-gradient(180deg, #06101a, #040a10);
  box-shadow:
    0 0 28px #00e5ff22,
    0 0 0 1px #7c4dff22 inset;
  position:relative;
  overflow:hidden;
}
.frame:before{
  content:"";
  position:absolute;
  inset:-2px;
  background:
    linear-gradient(90deg, transparent 0 20%, var(--grid) 20% 21%, transparent 21% 40%, var(--grid) 40% 41%, transparent 41% 60%, var(--grid) 60% 61%, transparent 61% 80%, var(--grid) 80% 81%, transparent 81% 100%),
    linear-gradient(0deg, transparent 0 20%, var(--grid) 20% 21%, transparent 21% 40%, var(--grid) 40% 41%, transparent 41% 60%, var(--grid) 60% 61%, transparent 61% 80%, var(--grid) 80% 81%, transparent 81% 100%);
  opacity:.75;
  pointer-events:none;
  mask:linear-gradient(#000, transparent 70%);
}

.display{
  position:relative;
  border:1px solid #00e5ff55;
  border-radius:14px;
  padding:14px 14px 12px;
  background:rgba(2,8,12,.65);
  box-shadow:0 0 22px #00e5ff22 inset;
  margin-bottom:14px;
}
.expr{
  font-size:14px;
  opacity:.75;
  min-height:18px;
  word-wrap:break-word;
}
.out{
  font-size:34px;
  font-weight:650;
  letter-spacing:0.02em;
  margin-top:6px;
  word-break:break-all;
}

.keys{
  display:grid;
  grid-template-columns: repeat(4, 1fr);
  gap:10px;
}
.btn{
  appearance:none;
  border:1px solid #00e5ff3d;
  background:rgba(0,229,255,.05);
  color:var(--text);
  border-radius:14px;
  padding:14px 10px;
  font-size:16px;
  cursor:pointer;
  transition: transform .06s ease, box-shadow .15s ease, border-color .15s ease;
  box-shadow:0 0 0 1px #7c4dff14 inset;
}
.btn:hover{
  border-color:#00e5ff7a;
  box-shadow:0 0 18px #00e5ff18, 0 0 0 1px #7c4dff22 inset;
}
.btn:active{ transform: translateY(1px) }
.btn.op{ color: #b6fbff }
.btn.ac{ color:#ff8bb2; border-color:#ff4d7d55; background:rgba(255,77,125,.07) }
.btn.eq{
  grid-column: span 2;
  border-color:#00e5ffaa;
  background:linear-gradient(180deg, rgba(0,229,255,.18), rgba(124,77,255,.10));
  box-shadow:0 0 22px #00e5ff22, 0 0 0 1px #00e5ff33 inset;
}
.hint{
  margin-top:12px;
  font-size:12px;
  opacity:.75;
}
.shake{
  animation: shake .18s linear 0s 2;
}
@keyframes shake{
  0%{transform:translateX(0)}
  25%{transform:translateX(-3px)}
  50%{transform:translateX(3px)}
  75%{transform:translateX(-2px)}
  100%{transform:translateX(0)}
}