#content {
    transition: opacity 0.5s ease-in-out;
}

.fade-out {
    animation: fadeOut 0.5s forwards;
}

.fade-in {
    animation: fadeIn 0.5s forwards;
}

@keyframes fadeOut {
    from {
        opacity: 1;
        transform: translateY(0);
    }
    to {
        opacity: 0;
        transform: translateY(-20px);
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Loading animation */
#loading {
    display: flex;
    justify-content: center;
    align-items: center;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5); /* 取色于背景主题色 */
    z-index: 9999;
}

.loader {
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 40px;
    height: 40px;
    background-color: #ff0000; /* 初始颜色 */
    animation: rotate 1s infinite linear, colorChange 4s infinite linear;
}

@keyframes rotate {
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
}

@keyframes colorChange {
    0% {
        background-color: #ff0000;
    }
    25% {
        background-color: #00ff00;
    }
    50% {
        background-color: #0000ff;
    }
    75% {
        background-color: #ffff00;
    }
    100% {
        background-color: #ff0000;
    }
}