Menu.razor
@using Sandbox;
@using Sandbox.UI;

@inherits PanelComponent

<style>
    Hud {
        pointer-events: all;
        width: 100%;
        height: 100%;
    }

	.hello {
		margin: 100px;
		font-size: 32px;
		color: red;
		text-shadow: 2px 2px 10px  black}

	.goodbye {
		margin: 200px;
		font-size: 64px;
		color: green;
		text-shadow: 5px 5px 20px  black}
</style>

<root>
	<panel class="hello" onmousedown="@Play" >
		Hello Razer. Ti gondone: @SomeNumber
	</panel>

	@if(ShowGoodbye)
	{
		<panel class="goodbye">
			Goodbye Lads!
		</panel>
	}
</root>

@code
{
	private int SomeNumber = 32;
	private bool ShowGoodbye = false;

	private void Play()
	{
		Log.Error("SEX TIME!");
		ShowGoodbye = !ShowGoodbye;
	}
}