* {
  font-family: "Poppins", sans-serif;
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  background: linear-gradient(to right, #1f2937, #111827);
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
}

.container {
  background-color: #111827;
  padding: 30px;
  border-radius: 20px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.6);
  max-width: 350px;
  width: 100%;
}

.cals-text {
  margin-bottom: 20px;
  padding: 15px;
  background-color: #1f2937;
  border-radius: 12px;
  min-height: 60px;
}

.cals-text p {
  font-size: 2.5rem;
  text-align: right;
  color: #d1d5db;
  word-break: break-all;
}

button {
  font-size: 1.5rem;
  border: none;
  border-radius: 16px;
  cursor: pointer;
  height: 65px;
  width: 65px;
  transition: 0.2s;
}

button:hover {
  transform: scale(1.07);
  filter: brightness(1.2);
}

.cals-keys {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

.key-zero {
  grid-column: span 2;
  width: 100%;
  border-radius: 14px;
}

.key-operate {
  background-color: #14b8a6;
  color: #fff;
}

.key-others {
  background-color: #374151;
  color: #e5e7eb;
}

.numbers {
  background-color: #1f2937;
  color: #f3f4f6;
}

button:active {
  transform: scale(0.96);
}