Collapse
Animated collapse using HTML details.
        
            
            Collapse
         
    
    Show something
  
Code
 
 <details class="blue-collapse">
    <summary>
        <header class="blue-collapse-header d-flex">
            <div class="blue-collapse-chevron" aria-hidden="true">❯</div>
            Collapse
        </header>
    </summary>
    Show something
</details> Element with class blue-collapse-chevron will be rotated to 90deg by default. But you can also customize the rotation target position with the CSS variable --blue-collapse-chevron-rotate:
        
            Collapse
            
         
    
    Show something
  
Code
 
 <details class="blue-collapse">
    <summary>
        <header class="blue-collapse-header d-flex">
            Collapse
            <div class="blue-collapse-chevron" style="--blue-collapse-chevron-rotate: -90deg" aria-hidden="true">
                ❮
            </div>
        </header>
    </summary>
    Show something
</details> Combine with styling of Menu Item
  
Code
 
 <details class="blue-collapse">
    <summary class="blue-collapse-header blue-menu-item btn">
        <span class="blue-menu-item-icon" aria-hidden="true">☀️</span>
        <span class="blue-menu-item-label">Parent</span>
        <svg
            xmlns="http://www.w3.org/2000/svg"
            width="1em"
            height="1em"
            fill="currentColor"
            class="blue-menu-item-dropdown-toggle blue-collapse-chevron blue-menu-item-chevron ms-auto"
            style=" display: inline-block; vertical-align: -0.125em; transition: transform 0.2s;"
            viewBox="0 0 16 16"
        >
            <path
                fill-rule="evenodd"
                d="M4.646 1.646a.5.5 0 0 1 .708 0l6 6a.5.5 0 0 1 0 .708l-6 6a.5.5 0 0 1-.708-.708L10.293 8 4.646 2.354a.5.5 0 0 1 0-.708"
            />
        </svg>
    </summary>
    <div class="blue-menu-item-dropdown text-body" style="--blue-menu-item-dropdown-bg: var(--bs-body-bg)">
        <button type="button" class="blue-menu-item btn">
            <span class="blue-menu-item-icon" aria-hidden="true">🌍</span>
            <span class="blue-menu-item-label">Child</span>
        </button>
        <button type="button" class="blue-menu-item btn">
            <span class="blue-menu-item-icon" aria-hidden="true">🌑</span>
            <span class="blue-menu-item-label">Child 2</span>
        </button>
    </div>
</details> Menu Item and Collapse grouped
.blue-collapse-group let’s you group a collapse together with another UI element like a button that should come before the collapse summary.
Collapse sub menu
  
Code
 
 <div class="blue-collapse-group">
    <button type="button" class="blue-menu-item btn">
        <span class="blue-menu-item-icon" aria-hidden="true">☀️</span>
        <span class="blue-menu-item-label">Parent</span>
    </button>
    <details class="blue-collapse">
        <summary class="blue-collapse-header blue-menu-item btn">
            <span class="visually-hidden">Collapse sub menu</span>
            <svg
                xmlns="http://www.w3.org/2000/svg"
                width="1em"
                height="1em"
                fill="currentColor"
                class="blue-menu-item-dropdown-toggle blue-collapse-chevron blue-menu-item-chevron ms-auto"
                style=" display: inline-block; vertical-align: -0.125em; transition: transform 0.2s;"
                viewBox="0 0 16 16"
            >
                <path
                    fill-rule="evenodd"
                    d="M4.646 1.646a.5.5 0 0 1 .708 0l6 6a.5.5 0 0 1 0 .708l-6 6a.5.5 0 0 1-.708-.708L10.293 8 4.646 2.354a.5.5 0 0 1 0-.708"
                />
            </svg>
        </summary>
        <div class="blue-menu-item-dropdown text-body" style="--blue-menu-item-dropdown-bg: var(--bs-body-bg)">
            <button type="button" class="blue-menu-item btn">
                <span class="blue-menu-item-icon" aria-hidden="true">🌍</span>
                <span class="blue-menu-item-label">Child</span>
            </button>
            <button type="button" class="blue-menu-item btn">
                <span class="blue-menu-item-icon" aria-hidden="true">🌑</span>
                <span class="blue-menu-item-label">Child 2</span>
            </button>
        </div>
    </details>
</div>   
Code
 
 <div class="bg-body-secondary py-4" style="width: 16.563rem">
    <div class="blue-collapse-group blue-sidebar-visible-on-open">
        <div class="blue-menu-item-wrapper blue-menu-item-wrapper-208d4903-3a8c-4e7b-9b27-ba27782210f8">
            <button type="button" class="blue-menu-item btn">
                <span class="blue-menu-item-icon  " aria-hidden="true"
                    ><svg
                        xmlns="http://www.w3.org/2000/svg"
                        viewBox="0 0 10240 10240"
                        class="o-collection-icon"
                        width="1em"
                        height="1em"
                        fill="currentColor"
                    >
                        <path
                            fill=""
                            d="M1280 640l5230 0c352,0 656,126 905,375l1170 1170c249,249 375,553 375,905l0 6510 -7680 0 0 -8960zm5760 960l0 960 960 0 -960 -960zm-5120 -320l0 7680 6400 0 0 -5440c0,-176 -144,-320 -320,-320l-1600 0 0 -1600c0,-176 -144,-320 -320,-320l-4160 0z"
                        ></path></svg></span
                ><span class="blue-menu-item-label text-truncate ">Filter & Controls</span>
            </button>
        </div>
        <details class="blue-collapse " open="">
            <summary class="blue-collapse-header blue-menu-item btn ">
                <span class="blue-menu-item-label text-truncate visually-hidden">Öffnen</span
                ><svg
                    xmlns="http://www.w3.org/2000/svg"
                    width="1em"
                    height="1em"
                    fill="currentColor"
                    class="blue-menu-item-dropdown-toggle blue-collapse-chevron blue-menu-item-chevron ms-auto"
                    aria-hidden="true"
                    style=" display: inline-block; vertical-align: -0.125em; transition: transform 0.2s;"
                    viewBox="0 0 16 16"
                >
                    <path
                        fill-rule="evenodd"
                        d="M4.646 1.646a.5.5 0 0 1 .708 0l6 6a.5.5 0 0 1 0 .708l-6 6a.5.5 0 0 1-.708-.708L10.293 8 4.646 2.354a.5.5 0 0 1 0-.708"
                    />
                </svg>
            </summary>
            <div class="d-flex flex-column border-start position-relative ms-3">
                <a href="#" class="blue-menu-item btn" rel=""
                    ><span class="blue-menu-item-label text-truncate ">Listen</span></a
                >
                <a href="#" class="blue-menu-item btn" rel=""
                    ><span class="blue-menu-item-label text-truncate">Ablage von Filtercontrols in XAML</span></a
                >
            </div>
        </details>
    </div>
</div> Grab the code
When you don't use the entire Blue Web library, you can also just copy and paste the required code into your own project.
-  
Copy and paste the following code into your project. Source:  @/dist/styles/_collapse.scss