* {
    box-sizing: border-box;
}
body {
    margin: 0;
    font-family: sans-serif;
    background: #111;
    color: #fff;
    overflow: hidden;
}
.navbar {
    display: flex;
    background: #222;
    padding: 10px;
    justify-content: space-around;
}
.navbar button {
    background: none;
    border: none;
    color: #fff;
    font-size: 16px;
    cursor: pointer;
    padding: 10px 20px;
}
.navbar button.active {
    background: #555;
}
.container {
    display: flex;
    height: calc(100vh - 50px);
}
.sidebar {
    width: 200px;
    background: #1a1a1a;
    overflow: hidden;
    position: relative;
}
.submenu {
    position: absolute;
    width: 100%;
    top: 0;
    transition: top 0.3s ease;
}
.submenu-item {
    padding: 15px;
    cursor: pointer;
    opacity: 0.5;
    transition: opacity 0.3s, transform 0.3s;
}
.submenu-item.active {
    background: #333;
    opacity: 1;
    transform: scale(1.05);
}
.content {
    flex-grow: 1;
    padding: 20px;
    background: #222;
}
.content-section {
    display: none;
}
.content-section.active {
    display: block;
}