/* 公共样式 - 返回主界面按钮 */
nav.main-nav {
    position: fixed;
    top: 20px;
    left: 20px;
    z-index: 1000;
}

.back-to-main {
    display: inline-block;
    background-color: var(--primary-color);
    color: white;
    text-decoration: none;
    padding: 10px 15px;
    border-radius: 25px;
    font-weight: 500;
    transition: all 0.3s ease;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

.back-to-main:hover {
    background-color: var(--secondary-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15);
}

/* 背单词项目的返回按钮特殊样式 */
.back-btn {
    background-color: var(--primary-color);
    color: white;
    text-decoration: none;
    border: none;
    padding: 10px 20px;
    border-radius: 25px;
    cursor: pointer;
    font-weight: 500;
    transition: all 0.3s ease;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
}

.back-btn:hover {
    background-color: var(--secondary-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.15);
}