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

body {
    width: 100%;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background: linear-gradient(135deg, #1a1a1a, #2c3e50);
}

.calculator {
    background: rgba(255, 255, 255, 0.05);
    padding: 25px;
    border-radius: 20px;
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.3);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.display-container {
    background: rgba(0, 0, 0, 0.2);
    border-radius: 12px;
    margin-bottom: 20px;
    padding: 5px;
}

input {
    width: 100%;
    min-height: 70px;
    border: none;
    padding: 20px;
    background: transparent;
    font-family: 'Roboto Mono', monospace;
    font-size: 2rem;
    text-align: right;
    color: #ffffff;
    outline: none;
}

input::placeholder {
    color: rgba(255, 255, 255, 0.5);
}

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

button {
    border: none;
    width: 65px;
    height: 65px;
    border-radius: 16px;
    background: rgba(255, 255, 255, 0.05);
    color: white;
    font-size: 1.4rem;
    font-family: 'Roboto Mono', monospace;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    backdrop-filter: blur(5px);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

button:hover {
    background: rgba(255, 255, 255, 0.1);
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
}

button:active {
    transform: translateY(0);
}

.operator {
    color: #00ff88;
    font-weight: 600;
}

.special {
    color: #ff3860;
}

.equal-btn {
    background: linear-gradient(135deg, #00ff88, #00b36b);
    color: #1a1a1a;
    font-weight: 600;
}

.equal-btn:hover {
    background: linear-gradient(135deg, #00ff95, #00cc77);
}

/* Animations */
@keyframes buttonPress {
    0% { transform: scale(1); }
    50% { transform: scale(0.95); }
    100% { transform: scale(1); }
}

.button-press {
    animation: buttonPress 0.15s ease-in-out;
}

/* Responsive Design */
@media (max-width: 400px) {
    .calculator {
        padding: 15px;
    }
    
    button {
        width: 55px;
        height: 55px;
        font-size: 1.2rem;
    }
    
    input {
        font-size: 1.6rem;
        min-height: 60px;
    }
}