:root {
  --blue-main: #2f7dbd;
  --blue-light: #a8cde6;
  --calculator-bg: #eaf3f9;
  --button-bg: #f6f9fc;
  --button-border: #d9e6f2;
  --equal-button: #1f6fb2;
  --highlight-green: #2ecc71;
  --text-main: #1f2d3d;
  --text-secondary: #6b7c93;
}

body {
  margin: 0;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: linear-gradient(135deg, var(--blue-main), var(--blue-light));
  font-family: Arial, sans-serif;
}

.calculator {
  width: 330px;
  background: var(--calculator-bg);
  padding: 20px;
  border-radius: 25px;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.15);
}

.display-box {
  background: #fff;
  border-radius: 18px;
  padding: 15px;
  margin-bottom: 20px;
  text-align: left;
}

.calc-input {
  min-height: 22px;
  font-size: 14px;
  color: var(--text-secondary);
  word-wrap: break-word;
}

.calc-result {
  min-height: 40px;
  font-size: 32px;
  font-weight: bold;
  color: var(--text-main);
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 14px;
  justify-items: center;
}

.btn {
  width: 65px;
  height: 65px;
  border-radius: 50%;
  border: 1px solid var(--button-border);
  background: var(--button-bg);
  font-size: 18px;
  cursor: pointer;
  transition:
    background 0.3s,
    transform 0.1s;
}

.btn:hover {
  background: var(--blue-light);
}

.btn:active {
  transform: scale(0.95);
  background: var(--blue-main);
}

.btn.operator {
  color: var(--blue-main);
  font-weight: bold;
}

/* ===== زر = ياخذ عمودين ===== */
.btn.equal {
  grid-column: span 2;
  width: 100%; /* يملأ مساحة عمودين */
  height: 65px;
  background: var(--equal-button);
  color: #fff;
  border: 0;
  border-radius: 999px;
}

.btn.equal:hover {
  filter: brightness(1.06);
}

.btn.equal:active {
  transform: scale(0.98);
  background: var(--equal-button);
}