When developing Flash games this was a personal hell. Many keyboards are unable to process Up+Left+Space, usually meant for shooting at northeast. In this case

When developing Flash games this was a personal hell. Many keyboards are unable to process Up+Left+Space, usually meant for shooting at northeast. In this case one of the keys is simply ignored. Worse yet the other directions work, so you get a hard to diagnose bug. The users end blaming you for their character deaths and the overall experience is frustrating. The best solution I found was to use a different key for shooting, such as left Ctrl, 'a' or 'z'. If you ever wondered why you can't use the large button on your keyboard to trigger the main action in a game, blame your keyboard manufacturer.