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

body {
  font-family: Arial, sans-serif;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  gap: 30px;
  height: 100vh;
  padding: 30px;
  background: #f4f4f4;
}

.calculator {
  background: #fff;
  padding: 20px;
  border-radius: 10px;
  box-shadow: 0 5px 15px rgba(0,0,0,0.1);
  width: 260px;
}

#display {
  width: 100%;
  height: 50px;
  font-size: 2rem;
  text-align: right;
  padding: 10px;
  border: 2px solid #ccc;
  border-radius: 5px;
  margin-bottom: 20px;
  background: #f5f5f5;
}

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

button {
  font-size: 1.5rem;
  padding: 15px;
  border: none;
  background: #f0f0f0;
  border-radius: 5px;
  cursor: pointer;
  transition: 0.2s;
}

button:hover {
  background: #ddd;
}

button:active {
  background: #bbb;
}

.history {
  background: #fff;
  padding: 15px;
  border-radius: 10px;
  box-shadow: 0 5px 15px rgba(0,0,0,0.1);
  width: 200px;
  max-height: 400px;
  overflow-y: auto;
}

.history h2 {
  margin-bottom: 10px;
}

.history ul {
  list-style: none;
}

.history li {
  padding: 5px 0;
  font-size: 1rem;
  border-bottom: 1px solid #eee;
}