Thursday, 19 September 2013


Lately, I've been tuning the "Drop-Rate" of pickups in Scooter Boy.  It's actually a lot like handing out candy at Halloween.

Allow me to use this handy diagram to explain:

Too little Candy
Too much Candy
Not enough candy to go 'round - some people walk away empty handed.Everyone is all full of sugary goodness, and they don't want any more.

But that's not actually what I wanted to talk about today.

I wanted to talk about Pigeons.

The Pigeon Food Dance

There was a famous set of experiments back in the '30s that revolved around withholding candyfood from pigeons.  In one of these experiments, the amount of time between successive drops was random. It turns out that each of the pigeons developed a (unique) ritualistic food dance. In happy pigeon land, it was the completion of the dance which caused the food to appear.

Now the curious thing was, the time it took for the pigeon to complete the dance was slightly longer than the average time between drops.

So when the pigeon completed the dance, there was a better than 50/50 chance of getting food.  And if not, well repeating the dance a second time would surely do it!

(Have you ever timed how long it takes to reboot your computer when you've got Tech Support on the phone?) 

Random Drop Rates

For most of Scooter Boy's development,  I've been using random drop rates.  Power ups would appear, seemingly at random.  Sometimes you'd get lots, and sometimes you'd go ages without seeing any.

Worse still, changing the drop rate, by changing the percentage of a drop, was very clumsy. You'd double or quadruple the drop rate, play the game, and the results would be... well ... random... There was no way to tell if your change was making the game better.

In short, random drops, just aren't fun!

A Drop Rate Schedule

I'm in the process of changing all those drop-rate percentages into times. 30±10 seconds between drops.  Or 120±60.  It's so much more measurable. And it turns out, it's a lot more fun too.  As a player, it feels like the powerups are rewarding your effort.

So down with Mathematical Randomness! Lets make the game match the player's expectations. Lets put the fun first!

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