/* Body Styling */
body {
    margin-top: 40px;
    padding: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    font-family: 'Arial', sans-serif;
    background: linear-gradient(45deg, #0f2027, #203a43, #2c5364);
    animation: gradientShift 10s infinite alternate;
    overflow: hidden;
}

@keyframes gradientShift {
    0% {
        background: linear-gradient(45deg, #0f2027, #203a43, #2c5364);
    }
    50% {
        background: linear-gradient(45deg, #141e30, #243b55);
    }
    100% {
        background: linear-gradient(45deg, #2b5876, #4e4376);
    }
}

/* Calculator Container */
#calculator {
    background: #1f2937;
    border-radius: 15px;
    padding: 20px;
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.5), inset 0 0 15px rgba(255, 255, 255, 0.1);
    width: 340px;
    animation: slideDown 1.5s ease-in-out;
    transform: translateY(-100px);
}

@keyframes slideDown {
    0% {
        opacity: 0;
        transform: translateY(-200px);
    }
    100% {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Display Section */
#display {
    width: 100%;
    padding: 15px;
    font-size: 1.6rem;
    border: 2px solid #1dd1a1;
    border-radius: 8px;
    margin-bottom: 20px;
    text-align: right;
    background: #2c3e50;
    color: #ecf0f1;
    box-shadow: inset 0 0 10px rgba(0, 0, 0, 0.5);
    animation: borderGlow 2s infinite alternate;
}

@keyframes borderGlow {
    0% {
        border-color: #1dd1a1;
        box-shadow: 0 0 15px #1dd1a1;
    }
    50% {
        border-color: #ff9f43;
        box-shadow: 0 0 15px #ff9f43;
    }
    100% {
        border-color: #ff6b6b;
        box-shadow: 0 0 15px #ff6b6b;
    }
}

/* Button Section */
#keys {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

/* Individual Button Styling */
#keys button {
    padding: 15px;
    font-size: 1.2rem;
    border: none;
    border-radius: 10px;
    background: linear-gradient(45deg, #ff6b6b, #ff9f43);
    color: white;
    cursor: pointer;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
    animation: buttonPulse 2s infinite alternate;
}

@keyframes buttonPulse {
    0% {
        transform: scale(1);
        box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
    }
    50% {
        transform: scale(1.1);
        box-shadow: 0 10px 25px rgba(255, 155, 100, 0.4);
    }
    100% {
        transform: scale(1.05);
        box-shadow: 0 10px 25px rgba(255, 255, 255, 0.5);
    }
}

#keys button:hover {
    transform: scale(1.2) rotate(2deg);
    background: linear-gradient(45deg, #48dbfb, #0abde3);
    box-shadow: 0 10px 25px rgba(0, 255, 255, 0.5);
}

#keys button:active {
    transform: scale(1);
    background: #2c3e50;
    color: #1dd1a1;
    box-shadow: 0 5px 10px rgba(0, 0, 0, 0.3);
}

/* Special Buttons */
#keys button[value="="] {
    background: linear-gradient(45deg, #1dd1a1, #10ac84);
    font-weight: bold;
    animation: glow 2s infinite alternate;
}

@keyframes glow {
    0% {
        box-shadow: 0 0 10px #1dd1a1;
    }
    100% {
        box-shadow: 0 0 20px #10ac84;
    }
}

#keys button[value="AC"] {
    background: linear-gradient(45deg, #ee5253, #ff6b6b);
}

#keys button[value="Del"] {
    background: linear-gradient(45deg, #576574, #8395a7);
}

/* Footer Section */
body::after {
    content: "© 2024-2026  · Designed & Developed by Hasib Hasan.All rights reserved.";
    position: fixed;
    bottom: 15px;
    width: 100%;
    text-align: center;
    font-size: 1rem;
    color: #ecf0f1;
    font-weight: bold;
    animation: footerGlow 3s infinite alternate;
}

@keyframes footerGlow {
    0% {
        color: #1dd1a1;
        text-shadow: 0 0 10px #1dd1a1;
    }
    50% {
        color: #ff9f43;
        text-shadow: 0 0 15px #ff9f43;
    }
    100% {
        color: #ee5253;
        text-shadow: 0 0 20px #ee5253;
    }
}

/* Responsive Design */
@media screen and (max-width: 768px) {
    body {
        margin-top: 20px; /* Reduced margin for smaller screens */
    }

    #calculator {
        width: 90%; /* Make calculator width responsive */
        padding: 10px; /* Reduced padding */
    }

    #display {
        font-size: 1.4rem; /* Adjust font size for display */
        padding: 10px; /* Adjust padding */
    }

    #keys button {
        padding: 10px; /* Adjust button padding */
        font-size: 1rem; /* Adjust button font size */
    }

    #keys {
        grid-template-columns: repeat(3, 1fr); /* Change button layout */
    }
}

@media screen and (max-width: 480px) {
    #calculator {
        width: 95%; /* Further reduce width */
    }

    #display {
        font-size: 1.2rem; /* Further adjust font size */
    }

    #keys button {
        padding: 8px; /* Further adjust button padding */
        font-size: 0.9rem; /* Further adjust button font size */
    }

    #keys {
        grid-template-columns: repeat(2, 1fr); /* Adjust button layout for very small screens */
    }
}