IPT - A Virtual Approach IPT A Virtual Approach by Peter Whitehouse
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Go Speed Racer!

A Simple Timer-based Game

A single timer and a few images combine to result in a simple game.

speed_Racer_Form

Three windows METAFILES race across a form until one wins. The race action is controlled by a single timer, with some simple buttons to control gameplay.

The Components:

What follows is a list of components needed for this application, along with some properties that need to be set for those components. Be systematic and TIDY placing your components.

  • save your project, naming the FORM file lakeside.pas and the PROJECT file as speedy.dpr. change the CAPTION property of the form to Go Speed Racer!, change the NAME property of the form to read racetrack.
  • Add a BUTTON to the form, change it's NAME to quit and change it's CAPTION to read &Quit
  • Add a BUTTON to the form, change it's NAME to raceControl and change it's CAPTION to read &Start
  • Add a TIMER to the form, change it's NAME to raceTimer, change it's ENABLED property to FALSE, change it's INTERVAL to 1
  • Add a LABEL to the form, change it's NAME to info, change it's CAPTION property to read Go Speed Racer!, and change it's FONT pitch and colour to suit.
  • Add an IMAGE to the form, change it's NAME to car1, load the image red.wmf into it, set the STRETCH property toTRUE, position it on the form, then set it's LEFT property to 1. Change it's HEIGHT to 50, change it's WIDTH to 60. If your browser has screwy file associations, a zip file of all the graphics used is also available. JPGS are also available
  • Do the same as previous step for IMAGES called car2 (load green.wmf) and car3 (load blue.wmf)

The Event Handlers

There are a number of event handlers that are necessary for the successful operation of this project. The complication here is that we have to detect (and therefore react to) one or more images reaching the right-hand edge of the form...

Control Name Event Handler Code
raceControl.onClick
  if raceControl.caption = '&Start'
     then begin
            raceControl.caption := 'Sto&p';
            info.caption := 'Go Speed Racer!'
          end
     else raceControl.caption := '&Start';
  raceTimer.enabled := not(raceTimer.enabled);
  car1.left := 1;
  car2.left := 1;
  car3.left := 1
quit.onClick
  close;
raceTimer.onTimer
var racing : boolean;
begin
  car1.left := car1.left + random(3);
  car2.left := car2.left + random(3);
  car3.left := car3.left + random(3);
  racing  := not(((car1.left + car1.width) >= clientWidth) or
                 ((car2.left + car2.width) >= clientWidth) or
                 ((car3.left + car3.width) >= clientWidth));
  raceTimer.enabled := racing;
  if not racing
     then begin
            if (car1.left + car1.width) >= clientWidth
               then info.caption := 'Racer 1 WON!'
               else if (car2.left + car2.width) >= clientWidth
                        then info.caption := 'Racer 2 WON!'
                        else info.caption := 'Racer 3 WON!';
            raceControl.caption := '&Start';
          end;

end;
raceTrack.formCreate
  randomize;

 

Final Touches

COMPILE the program to check for errors of 'SYNTAX', fix any that show, then RUN it to check it works correctly. Check it terminates correctly as one car hits the right-hand edge of the form. RaceControl.caption and info.caption should change at the end of a race.

Set the COLOR property of the form (ie. racetrack.color) to black to improve the animation.

Experts would realise that the current project does not allow ties (or rather ignores them, reporting only the first racer (in the list of 1..3) that has finished. A good addition to this system would be the correct reporting of ties

 

wonko@wonko.info
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