Why is my AppleScript not working? Making an AppleScript but for some reason it isn't working. Any ideas why not?

delay 1
set volume 1
say "Hello " &amp; (do shell script "whoami") using "Whisper"
say "Do you want to play a game?" using "Whisper"
display dialog "Do you want to play a game?" buttons {"Yes", "No"} default button 1
if the button returned of the result is "Yes" then
-- say "Bwahahahaha!"
else
-- display dialog "Big mistake" &amp; (do shell script "whoami")
end if
Works for me, but I had to set volume 6 to make it audible.

"Big mistake" should be "Big mistake " -- that space matters.