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

body {
    height: 100vh;
    width: 100vw;
    background: linear-gradient(145deg, #1a1a1d, #4e4e50);
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-evenly;
    color: #ffffff;
}

.container {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-template-rows: repeat(7, auto);
    gap: 10px;
    border-radius: 20px;
    padding: 20px;
    background: #222831;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.4), 0 -4px 15px rgba(255, 255, 255, 0.1) inset;
    width: 90%;
    max-width: 400px;
}

.expression,
.display {
    grid-column: span 4;
}

.expression input,
.display input {
    width: 100%;
    height: 60px;
    padding: 10px;
    text-align: right;
    border: none;
    border-radius: 10px;
    font-size: 20px;
    font-weight: 600;
    color: #ffffff;
    background: #393e46;
    box-shadow: inset 0 -3px 8px rgba(0, 0, 0, 0.5);
    outline: none;
}

.display input {
    font-size: 28px;
    height: 70px;
    background: #3e444e;
    box-shadow: inset 0 -4px 10px rgba(0, 0, 0, 0.7);
}


button {
    width: 70px;
    height: 70px;
    border: none;
    border-radius: 50%;
    font-size: 24px;
    font-weight: bold;
    color: #ffffff;
    background: linear-gradient(145deg, #3a4b59, #2b333b);
    box-shadow: 0 6px 15px rgba(0, 0, 0, 0.4);
    cursor: pointer;
    transition: transform 0.2s, background-color 0.2s;
}

button:hover {
    transform: translateY(-3px);
    background-color: #5a6b7c;
}

button:active {
    transform: translateY(0);
    box-shadow: inset 0 4px 10px rgba(0, 0, 0, 0.5);
}

.green {
    background: linear-gradient(145deg, #2ecc71, #27ae60);
    box-shadow: 0 6px 15px rgba(46, 204, 113, 0.4);
}

.green:hover {
    background-color: #28a745;
}

.orange {
    background: linear-gradient(145deg, #e74c3c, #c0392b);
    box-shadow: 0 6px 15px rgba(231, 76, 60, 0.4);
}

.orange:hover {
    background-color: #d63031;
}
.clear_history{
  background-color: initial;
  background-image: linear-gradient(-180deg, #00D775, #00BD68);
  border-radius: 5px;
  box-shadow: rgba(0, 0, 0, 0.1) 0 2px 4px;
  color: #FFFFFF;
  cursor: pointer;
  display: inline-block;
  height: 44px;
  line-height: 44px;
  outline: 0;
  overflow: hidden;
  padding: 0 20px;
  pointer-events: auto;
  position: relative;
  text-align: center;
  touch-action: manipulation;
  user-select: none;
  -webkit-user-select: none;
  vertical-align: top;
  white-space: nowrap;
  width: 100%;
  z-index: 9;
  border: 0;
}

.button-41:hover {
  background: #00bd68;
}


@media (max-width: 768px) {
    .container {
        gap: 8px;
        grid-template-columns: repeat(4, auto);
    }

    button {
        width: 60px;
        height: 60px;
        font-size: 20px;
    }

    .expression input,
    .display input {
        height: 50px;
        font-size: 18px;
    }
}

@media (max-width: 480px) {
    .container {
        gap: 5px;
        grid-template-columns: repeat(4, auto);
    }

    button {
        width: 50px;
        height: 50px;
        font-size: 18px;
    }

    .expression input,
    .display input {
        height: 45px;
        font-size: 16px;
    }
}