:root {
  --bg: var(--tg-theme-bg-color, #14161a);
  --secondary-bg: var(--tg-theme-secondary-bg-color, #1c1f24);
  --text: var(--tg-theme-text-color, #f2f3f5);
  --hint: var(--tg-theme-hint-color, #7d848f);
  --accent: var(--tg-theme-button-color, #3390ec);
  --accent-text: var(--tg-theme-button-text-color, #ffffff);
  --key-num: #262a31;
  --key-num-hover: #30343c;
  --key-op: var(--accent);
  --key-fn: #3a3f47;
  --radius: 20px;
}
* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
html, body {
  margin: 0;
  height: 100%;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Display", "Segoe UI", Roboto, sans-serif;
  overscroll-behavior: none;
}
.app {
  max-width: 480px;
  margin: 0 auto;
  padding: 14px 16px 24px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
.topbar {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 6px 2px 18px;
}
.topbar h1 {
  font-size: 16px;
  font-weight: 600;
  margin: 0;
  letter-spacing: 0.2px;
  flex: 1;
}
.dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #3ddc84;
  box-shadow: 0 0 0 3px rgba(61, 220, 132, 0.15);
}
.status {
  font-size: 11px;
  color: var(--hint);
  border: 1px solid rgba(125,132,143,0.35);
  padding: 3px 8px;
  border-radius: 999px;
}
.display {
  background: var(--secondary-bg);
  border-radius: var(--radius);
  padding: 28px 20px 22px;
  text-align: right;
  margin-bottom: 14px;
  min-height: 130px;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
}
.expr {
  font-size: 15px;
  color: var(--hint);
  min-height: 18px;
  word-break: break-all;
}
.result {
  font-size: 44px;
  font-weight: 600;
  line-height: 1.15;
  word-break: break-all;
  font-variant-numeric: tabular-nums;
}
.pad {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  flex: 1;
}
.key {
  border: none;
  border-radius: 16px;
  font-size: 22px;
  font-weight: 500;
  padding: 20px 0;
  color: var(--text);
  background: var(--key-num);
  cursor: pointer;
  transition: transform 0.06s ease, filter 0.15s ease;
}
.key:active {
  transform: scale(0.95);
  filter: brightness(1.15);
}
.key.fn {
  background: var(--key-fn);
  color: var(--text);
  font-size: 19px;
}
.key.op {
  background: var(--key-op);
  color: var(--accent-text);
  font-size: 24px;
}
.key.eq {
  background: var(--key-op);
  filter: saturate(1.3);
}
.key.zero {
  grid-column: span 1;
}
.hint {
  font-size: 11.5px;
  color: var(--hint);
  text-align: center;
  margin: 16px 4px 0;
  line-height: 1.5;
}