By using reset() with the parentheses, you are actually calling the reset function and inserting its return value, which is Void.

Instead, you want to use a reference to the reset function so that the Button action will call it for you. So:

Button("Restart", action: reset)

And just FYI, you don't need to include a return type when a function doesn't return anything.

func reset() { // no need for -> Void here
//blah blah blah
}