Space Explorer v.3 - Space Car Bouncing

Flash Tutorials - Herong's Tutorial Examples

∟Space Explorer v.3 - Space Car Bouncing

This section provides a tutorial example on how to use ActionScript 3 statement blocks in SWFC script file to build my Space Explorer - Version 3: the space car is wondering and bouncing between walls!

In Space Explorer Version 2, the space car will go out of the space boundary if you wait for a few minutes.

For Version 3, space_explorer_3.sc, I am trying to make space car bouncing back whenever it reaches a boundary:

#- space_explorer_3.sc
#- Copyright (c) 2014 by Dr. Herong Yang, herongyang.com
#
.flash bbox=400x400 background=#000044 fps=12
.circle space_car r=6 line=8 color=#cccccc fill=#ff0000

.frame 1
   .put space_car
   .action:
      _root.bbox_size = 400;
      _root.car_size = 20;
      _root.car_radius = 6;
      _root.x_acc_factor = 0.5;
      _root.y_acc_factor = 0.5;

      // car center position and speed
      _root.x_pos = 10;
      _root.y_pos = 10;
      _root.x_speed = 1.0;
      _root.y_speed = 0.5;

      // car center moving boundaries
      _root.x_min = 0.5*_root.car_size;
      _root.y_min = 0.5*_root.car_size;
      _root.x_max = _root.bbox_size - 0.5*_root.car_size;
      _root.y_max = _root.bbox_size - 0.5*_root.car_size;

      // top left corner is the anchor
      _x = _root.x_pos-_root.car_radius;
      _y = _root.y_pos-_root.car_radius;
   .end

.frame 2
   .action:
      _root.x_speed += _root.x_acc_factor*(Math.random()-0.50);
      _root.y_speed += _root.y_acc_factor*(Math.random()-0.50);

      _root.x_pos += _root.x_speed;
      _root.y_pos += _root.y_speed;

      // build bouncing walls
      if (_root.x_pos < _root.x_min) {
         _root.x_pos = 2*_root.x_min - _root.x_pos;
         _root.x_speed = - _root.x_speed;
      }
      if (_root.y_pos < _root.y_min) {
         _root.y_pos = 2*_root.y_min - _root.y_pos;
         _root.y_speed = - _root.y_speed;
      }
      if (_root.x_pos > _root.x_max) {
         _root.x_pos = 2*_root.x_max - _root.x_pos;
         _root.x_speed = - _root.x_speed;
      }
      if (_root.y_pos > _root.y_max) {
         _root.y_pos = 2*_root.y_max - _root.y_pos;
         _root.y_speed = - _root.y_speed;
      }

      _x = _root.x_pos-_root.car_radius;
      _y = _root.y_pos-_root.car_radius;
   .end
   
.frame 3
   .action:
      gotoFrame(1); // index=0 is for frame 1
      play();
   .end

.end

Note that Flash Player uses the top left corner as the anchor to put objects on the frame. But it is much easier to use the center of the circle to calculate bouncing walls.

Compile space_explorer_3.sc and generate the HTML code:

C:\herong>\local\SWFTools\swfc.exe space_explorer_3.sc 
   -o space_explorer_3.swf

C:\herong>\local\SWFTools\swfdump.exe -E space_explorer_3.swf
   > space_explorer_3.html