The one command a P&P RPG player needs from PowerShell

rollingdice.ps1

$ExecutionContext.InvokeCommand.CommandNotFoundAction = {
	param (
		[string]
		$CommandName,
		
		[System.Management.Automation.CommandLookupEventArgs]
		$Lookup
	)
	
	if ($CommandName -match '^(\d+)[WD](\d+)$')
	{
		$Lookup.StopSearch = $true
		$Lookup.Command = (Get-Command Invoke-DiceRoll)
		$Lookup.CommandScriptBlock = [scriptblock]::Create("Invoke-DiceRoll -Count $($matches[1]) -Size $($matches[2])")
	}
}

function Invoke-DiceRoll
{
	[CmdletBinding()]
	param (
		[int]
		$Count = 1,
		
		[int]
		$Size = 20
	)
	
	$results = foreach ($number in (1 .. $Count))
	{
		1..$Size | Get-Random
	}
	($results | Measure-Object -Sum).Sum
}