Having 1 button for multiple purposes

Question

Consider the following: you have a space invaders game. The 'hero' has 2 abilities - a normal attack which shoots standard bolts of whatever and a special attack which hits harder. The special attack can't be spammed.

There are a lot of ways to approach it: Number of times it can be used per level. It will use energy which is slowly regenerated and many more, but for our example let's consider that the 'hero' will not have any of those options and that the only possibilities are:

1) The ability must be charged

2) The ability has a cool down.

The question is: "What is the difference to the player when having 1 button per ability and multiple abilities per button?"

Of course, by this point I have to share that our imaginary game is not made for touch screens (Since if it was then it is pretty obvious that you want as little buttons as possible)

What I can think of is that when holding the button to "charge" it will give the player the impression that something strong is going to be unleashed. The downside of this is that this locks down the possibility to shoot the power up in the middle of combat.

Answer 1

This reminds me of a fairly well known usability story, where a conference was disrupted because the projector had a single button. The button would move forward a slide if pressed for a short time, or back a slide if pressed for longer, but of course this was not obvious to the presenters. Source: here

Pros:

• It's just one button - nobody will complain that their fingers slipped and they couldn't understand your complex keymap (especially nice for those new to PC games)
• Personally I think it feels cool to have one button do multiple things

Cons:

• On almost anything games are developed for, using just one button for multiple functions which may not be obvious could seem like an unnecessary limitation - a cool factor that might not be worth the effort for players when two buttons would be so much simpler
• There are always going to be people who are less able to use a fast-paced-tap vs. hold distinction, as well as those with various disabilities, people who use keyboard helpers such as StickyKeys, etc - these people may only have easy access to one of the multiple abilities
• People don't always read/understand the manual or instructions, so making the distinction obvious using the gameplay only could be difficult
• As you said yourself, the abilities must not need to be performed at the same time, as this won't really be possible

I think you could potentially avoid most of the cons and maximise the pros by some visual indication of whether a given input was going to result in ability X or Y, perhaps X if released quickly, with a bar filling as they held the key longer and a blip when Y was ready. Making the Y ability available on another key by default, or having an option to do so, would mean that people with slower reactions or other obstacles could still play the game. On the point of performing ability X while 'charging' ability Y, I would suggest either timers which allow small breaks in the charging (to release it for no longer than n milliseconds, thus using the other ability), or a charge bar which goes down much slower than it goes up, allowing the button to be released, and charging resumed at the player's discretion. (These two solutions might only be semantically different.)

Answer 2

you can afford to use multiple buttons if you're explicitly avoiding touch screens

There are several understood ways to make 1 button do multiple things:

(on screen buttons)

• double clicking
• left vs right clicking
• holding down vs pressing

(keys)

• ctrl + key
• shift + key
• holding down vs pressing

You don't want users to accidentally or unintentionally release the special, so however you activate it, it has to be very explicit.

I think multiple buttons (but as few as possible, in this case 2)

button1 could be used to spam the normal attack, and button2 to fire special