* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: Arial, sans-serif;
  line-height: 1.6;
  background-color: #1a202e;
}

img {
  max-width: 100%;
  display: block;
}

a {
  text-decoration: none;
  color: black;
}

ul {
  list-style: none;
}

.outer_cal {
  max-width: 26%;
  margin: 50px auto;
  background: linear-gradient(145deg, #0f1a2b, #0a1322);
  border-radius: 50px;
  padding: 5px;
  box-shadow:
    0 0 25px rgba(0, 0, 0, 0.8),
    0 0 60px rgba(0, 150, 255, 0.1);
  border: 5px solid rgba(255, 255, 255, 0.08);
  box-shadow:
    10px 10px 30px rgba(0, 0, 0, 0.9),
    -10px -10px 30px rgba(255, 255, 255, 0.05);
}
.inner_cal {
  display: flex;
  flex-direction: column;
  background-color: #1a202e;
  padding: 20px;
  border-radius: 50px;
  gap: 40px;
}
.result_show {
  max-width: 100%;
  background: linear-gradient(160deg, #1e2436, #161b28);
  border-radius: 24px;
  min-height: 180px;
  padding: 24px 20px 20px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  align-items: flex-end;
  gap: 10px;
  box-shadow:
    inset 0 2px 8px rgba(0, 0, 0, 0.6),
    inset 0 -1px 0 rgba(255, 255, 255, 0.04),
    0 1px 0 rgba(255, 255, 255, 0.06);
  overflow: hidden;
}

.expression {
  color: #6b7280;
  font-size: 30px;
  font-weight: 400;
  letter-spacing: 0.5px;
  opacity: 0.8;
}

.result {
  color: #ffffff;
  font-size: 52px;
  font-weight: 300;
  letter-spacing: -1.5px;
  line-height: 1;
  word-break: break-all;
  text-align: right;
}
.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

/* ── BASE BUTTON ── */
.btn {
  padding: 0;
  height: 72px;
  font-size: 22px;
  font-weight: 500;
  border: none;
  border-radius: 18px;
  color: #fff;
  cursor: pointer;
  position: relative;
  font-size: 30px;
  font-weight: 500;
  background: linear-gradient(145deg, #252c3d, #1a2030);
  box-shadow:
    5px 5px 12px rgba(0, 0, 0, 0.7),
    -2px -2px 6px rgba(255, 255, 255, 0.05),
    inset 0 1px 0 rgba(255, 255, 255, 0.07),
    inset 0 -1px 0 rgba(0, 0, 0, 0.4);

  transition: all 0.1s ease;
}

.btn:active {
  box-shadow:
    2px 2px 6px rgba(0, 0, 0, 0.7),
    -1px -1px 3px rgba(255, 255, 255, 0.03),
    inset 0 2px 6px rgba(0, 0, 0, 0.5),
    inset 0 -1px 0 rgba(255, 255, 255, 0.03);
  transform: translateY(1px);
}

.operator_btn {
  background: linear-gradient(145deg, #f5832e, #d4611a) !important;
  box-shadow:
    5px 5px 12px rgba(0, 0, 0, 0.6),
    -2px -2px 6px rgba(255, 160, 60, 0.15),
    inset 0 1px 0 rgba(255, 200, 120, 0.3),
    inset 0 -2px 0 rgba(0, 0, 0, 0.25) !important;
}

.operator_btn:active {
  background: linear-gradient(145deg, #d4611a, #b85010) !important;
  box-shadow:
    2px 2px 6px rgba(0, 0, 0, 0.6),
    inset 0 2px 6px rgba(0, 0, 0, 0.4),
    inset 0 -1px 0 rgba(255, 150, 60, 0.1) !important;
}

/* ── AC orange text ── */
#clear {
  color: #ef7223;
}

/* ── ZERO BUTTON (spans 2 cols) ── */
.zero_btn {
  grid-column: span 2;
  display: flex;
  justify-content: flex-start;
  padding-left: 26px;
  align-items: center;
}