body {
    margin: 0;
    height: 100vh;
    overflow: hidden;
    font-family: "Segoe UI", sans-serif;
    background:
        linear-gradient(rgba(255,255,255,0.05), rgba(0,0,0,0.1)),
        linear-gradient(to bottom, #0086e6, #0057a8);
    display: flex;
    justify-content: center;
    align-items: center;
}

/* Main Window */
.window {
    width: 520px;
    background: #f2f2f2;
    border: 1px solid #0a5fa8;
    box-shadow:
        0 0 0 1px rgba(255,255,255,0.2),
        0 10px 40px rgba(0,0,0,0.5);
    animation: popin 0.25s ease;
}

/* Windows 8.1 Title Bar */
.titlebar {
    background: linear-gradient(to bottom, #0f8ce9, #0078d7);
    color: white;
    padding: 10px 12px;
    font-size: 14px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    user-select: none;
}

/* Fake Window Buttons */
.buttons {
    display: flex;
}

.buttons div {
    width: 42px;
    height: 22px;
    margin-left: 2px;
    background: rgba(255,255,255,0.15);
    transition: 0.15s;
}

.buttons div:hover {
    background: rgba(255,255,255,0.3);
}

/* Content */
.content {
    padding: 45px;
    text-align: center;
}

h1 {
    color: #222;
    margin-bottom: 35px;
    font-weight: 300;
    font-size: 34px;
}

/* Download Button */
.download-btn {
    background: linear-gradient(to bottom, #1695ff, #0078d7);
    border: 1px solid #005ca8;
    color: white;
    padding: 18px 50px;
    font-size: 24px;
    cursor: pointer;
    transition: 0.15s;
    box-shadow:
        inset 0 1px rgba(255,255,255,0.3),
        0 3px 8px rgba(0,0,0,0.25);
}

.download-btn:hover {
    background: linear-gradient(to bottom, #2ba0ff, #1188eb);
    transform: scale(1.03);
}

.download-btn:active {
    transform: scale(0.97);
}

/* Popup Window */
.popup {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 390px;
    background: #f2f2f2;
    border: 1px solid #0078d7;
    display: none;
    box-shadow:
        0 0 0 1px rgba(255,255,255,0.2),
        0 15px 50px rgba(0,0,0,0.7);
    animation: popupAnim 0.2s ease;
}

.popup-title {
    background: linear-gradient(to bottom, #0f8ce9, #0078d7);
    color: white;
    padding: 10px;
    font-size: 14px;
}

.popup-content {
    padding: 35px;
    color: #111;
    font-size: 20px;
    text-align: center;
}

/* OK Button */
.ok-btn {
    margin-top: 22px;
    background: linear-gradient(to bottom, #1695ff, #0078d7);
    border: 1px solid #005ca8;
    color: white;
    padding: 10px 30px;
    cursor: pointer;
    font-size: 16px;
}

.ok-btn:hover {
    background: linear-gradient(to bottom, #2ba0ff, #1188eb);
}

/* Animations */
@keyframes popin {
    from {
        transform: scale(0.9);
        opacity: 0;
    }

    to {
        transform: scale(1);
        opacity: 1;
    }
}

@keyframes popupAnim {
    from {
        opacity: 0;
        transform: translate(-50%, -45%);
    }

    to {
        opacity: 1;
        transform: translate(-50%, -50%);
    }
}