<span class="spoiler">
    <u>@ChildContent</u>
</span>

<style>
    .spoiler {
        color: black;
        background-color: black;
    }

    u {
        text-decoration-color: inherit;
        text-decoration-thickness:1px;
    }

    .spoiler:hover {
        color: inherit;
        background-color: inherit;
    }

</style>

@code {

    [Parameter]
    public RenderFragment ChildContent { get; set; } = default!;

}