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

body {
    background: #0f0f1a;
    color: #e0e0e0;
    line-height: 1.6;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    min-height: 100vh;
}

/* Page Title */
h1 {
    color: #7a5cff;
    text-align: center;
    margin: 2rem 0;
    text-shadow: 0 0 10px rgba(122, 92, 255, 0.6);
}

/* Calculator Container */
.calculator-container {
    text-align: center;
}

/* Calculator */
.calculator {
    background: #1b1b2f;
    padding: 2rem;
    border-radius: 12px;
    max-width: 350px;
    margin: auto;
}

/* Display */
.display {
    width: 100%;
    height: 50px;
    margin-bottom: 1rem;
    border-radius: 6px;
    border: none;
    padding: 0.5rem;
    font-size: 1.5rem;
    text-align: right;
    background: #0f0f1a;
    color: #fff;
    box-shadow: inset 0 0 5px rgba(0,198,255,0.7);
}

/* Buttons Grid */
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 1rem;
}

/* Button Styles */
.btn {
    padding: 1rem;
    font-size: 1.2rem;
    border: none;
    border-radius: 8px;
    background: linear-gradient(45deg, #7a5cff, #00c6ff);
    color: #000;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s ease;
}

/* Button Hover Glow */
.btn:hover {
    transform: translateY(-5px);
    animation: glowing 1.6s infinite alternate;
}

/* Special Buttons */
.operator {
    background: linear-gradient(45deg, #ff4d6d, #ffb84d);
}

.clear {
    background: linear-gradient(45deg, #ff3f3f, #ff6f6f);
}

.equal {
    grid-column: span 4;
    background: linear-gradient(45deg, #7aff95, #00ffa0);
}

/* Glowing Animation */
@keyframes glowing {
    from {
        box-shadow: 0 0 5px rgba(170,0,255,0.6),
                    0 0 15px rgba(170,0,255,0.7);
    }
    to {
        box-shadow: 0 0 20px rgba(0,198,255,0.7),
                    0 0 40px rgba(0,198,255,0.9);
    }
}

/* Back Button */
.back-link {
    display: inline-block;
    padding: 0.6rem 1.2rem;
    background: linear-gradient(45deg, #7a5cff, #00c6ff);
    color: #000;
    font-weight: 600;
    font-size: 1rem;
    border-radius: 6px;
    text-decoration: none;
    text-align: center;
    margin: 2rem auto;
    transition: transform 0.3s ease;
}

.back-link:hover {
    transform: scale(1.05);
    animation: glowing 1.6s infinite alternate;
}