CODING

Tutorial
WALKTHROUGH
>STEP-02
Make the box bottoms
A band clamp was used to ensure the sides were
perpendicular to the base as they were glued together.
We used Gorilla glue and moistened the wood before
applying the glue. After about two hours, the clamp
was removed and excess glue cut off with a scalpel.
Drill the base with an M3 drill for both the corner hex
pillars and the nuts and bolts for the ball rests.
The resources
The graphics for the horses were taken from a cutout
supplement, printed in the Boston Sunday Globe
in September 1905, by RF Ayers; this is now well out
of copyright. This cut-out featured two horses in
mid-gallop, curiously carrying the numbers ‘one’
and ‘three’ on the saddle cloth. We have named the
first horse ‘Raspberry Rake’ and the third ‘Not Quite
Pi’, which we thought were suitable racing names.
These horses were cut out electronically in a graphics
package, and the background made transparent.
Then they were reduced to just 196 by 136 pixels. The
graphic of a track was drawn with a finishing post and
line, and then a front rail was drawn with transparent
sections between the rails. Finally, a sequence of
graphics was drawn to indicate the required path of
the ball bearing for each challenge. We also gathered
a series of sound effects from the internet to help the
game along.
Playing the game
The graphic by the horse name shows the two points
the ball bearing must visit to advance the horse. The
filled orange circle indicates the current target for
your ball: only when you visit the start position, and
then the end one, will the horse move. When you
have just visited the start position, there will be a
horse whinnying sound, and then you get the horse
galloping sound and animation when you visit the
last position. When the horse advances, not only
does it go forward, but it also moves slightly up and
down in a galloping motion; this mimics the original
fairground version. When one of the horses crosses
52 January 2017
raspberrypi.org/magpi