:root{
  --bg: #0f1117;
  --card: #161a22cc;
  --glass: rgba(255,255,255,0.06);
  --text: #e8eefc;
  --sub: #9fb0d3;
  --accent: #7c9cff;
  --accent-2: #55e6a5;
  --op: #2c3550;
  --op-active: #3b4670;
  --util: #263043;
  --equal: #5c7cfa;
  --shadow: 0 10px 30px rgba(0,0,0,.35);
}

body.theme-light{
  --bg: #eef2fb;
  --card: #ffffffcc;
  --glass: rgba(0,0,0,0.04);
  --text: #0f1320;
  --sub: #51607c;
  --accent: #4c6ef5;
  --accent-2: #12b886;
  --op: #e8edfb;
  --op-active: #dfe7ff;
  --util: #e9eef9;
  --equal: #4c6ef5;
  --shadow: 0 8px 22px rgba(18, 38, 75, .18);
}

*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;
  background:
    radial-gradient(1200px 600px at 10% 10%, #1b2140 0%, transparent 60%),
    radial-gradient(1000px 500px at 90% 20%, #1b403a 0%, transparent 60%),
    var(--bg);
  color:var(--text);
  font: 500 16px/1.25 "Inter", system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  display:flex;
  flex-direction:column;
  align-items:center;
}

.app{
  width: min(980px, 92vw);
  margin: 24px auto 12px;
  display:grid;
  grid-template-columns: 1fr 320px;
  gap: 20px;
}

.topbar{
  grid-column:1 / -1;
  display:flex;
  align-items:center;
  justify-content:space-between;
  background:linear-gradient(180deg, var(--card), transparent),
             var(--glass);
  backdrop-filter: blur(12px);
  border: 1px solid rgba(255,255,255,.08);
  border-radius: 16px;
  padding: 14px 16px;
  box-shadow: var(--shadow);
}

.brand{
  margin:0;
  font-size: clamp(18px, 2vw, 22px);
  letter-spacing:.3px;
}

.actions button{
  margin-left: 8px;
  border: 1px solid rgba(255,255,255,.10);
  background: var(--glass);
  color: var(--text);
  border-radius: 10px;
  padding: 8px 10px;
  cursor:pointer;
  transition: transform .08s ease, background .2s ease;
}
.actions button:hover{ transform: translateY(-1px); }

.calculator{
  background: linear-gradient(180deg, var(--card), transparent), var(--glass);
  border: 1px solid rgba(255,255,255,.08);
  border-radius: 18px;
  padding: 18px;
  box-shadow: var(--shadow);
}

.display{
  min-height: 120px;
  border-radius: 14px;
  padding: 14px;
  background: linear-gradient(180deg, rgba(255,255,255,.06), transparent);
  border: 1px solid rgba(255,255,255,.06);
  box-shadow: inset 0 1px 2px rgba(0,0,0,.2);
  display:flex;
  flex-direction:column;
  justify-content:flex-end;
  overflow:hidden;
}

.expression{
  color: var(--sub);
  min-height: 28px;
  word-wrap: break-word;
  word-break: break-all;
  text-align: right;
  font-size: clamp(14px, 2.2vw, 16px);
}

.result{
  font-weight: 700;
  text-align:right;
  font-size: clamp(28px, 4.4vw, 40px);
  margin-top: 6px;
}

.keypad{
  margin-top: 14px;
  display:grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

.key{
  height: 58px;
  border-radius: 14px;
  border: 1px solid rgba(255,255,255,.08);
  background: linear-gradient(180deg, rgba(255,255,255,.05), transparent),
              var(--op);
  color: var(--text);
  font-size: 18px;
  letter-spacing:.3px;
  cursor:pointer;
  box-shadow: 0 6px 18px rgba(0,0,0,.25);
  transition: transform .05s ease, filter .15s ease, background .15s ease;
}
.key:hover{ filter: brightness(1.05); }
.key:active{ transform: translateY(1px) scale(.995); }

.key.op{
  background: linear-gradient(180deg, rgba(255,255,255,.10), transparent),
              var(--op-active);
  border-color: rgba(124,156,255,.35);
}

.key.util{
  background: linear-gradient(180deg, rgba(255,255,255,.06), transparent),
              var(--util);
}

.key.zero{
  grid-column: span 2;
}

.key.equal{
  background: linear-gradient(180deg, rgba(255,255,255,.18), transparent),
              var(--equal);
  border-color: rgba(255,255,255,.25);
  font-weight: 700;
}

.history{
  background: linear-gradient(180deg, var(--card), transparent), var(--glass);
  border: 1px solid rgba(255,255,255,.08);
  border-radius: 18px;
  padding: 16px;
  box-shadow: var(--shadow);
  max-height: 640px;
  overflow: hidden;
  display:flex;
  flex-direction:column;
}

.history-head{
  display:flex;
  align-items:center;
  justify-content:space-between;
  margin-bottom: 6px;
}
.history-head h2{ margin: 0; font-size: 16px; color: var(--sub); }
.history-head .link{
  background: transparent; border: none; color: var(--accent);
  cursor:pointer; font-weight: 600;
}

.history-list{
  list-style: none; margin: 0; padding: 0;
  overflow: auto;
  flex:1;
  border-top: 1px dashed rgba(255,255,255,.10);
}
.history-list li{
  padding: 10px 2px;
  border-bottom: 1px dashed rgba(255,255,255,.06);
  display:flex; justify-content:space-between; gap: 12px;
}
.history-list .expr{ color: var(--sub); font-size: 14px; }
.history-list .val{ font-weight: 700; }

.credit{ margin: 8px 0 18px; color: var(--sub); }

@media (max-width: 900px){
  .app{
    grid-template-columns: 1fr;
  }
  .history{
    display:none;
  }
  .history.open{
    display:flex;
    order: 3;
  }
}