function simGroup::pt( %this )
{
	// loop hell protection
	cancel( %this.pt );

	// erase previous frame
	%this.erasePong();
	%this.eraseScore( 0 );
	%this.eraseScore( 1 );
	%this.erasePaddle( 0 );
	%this.erasePaddle( 1 );

	// move AI paddles
	%this.movePaddle( 0 );
	%this.movePaddle( 1 );

	// fix AI paddles
	for ( %i = 0 ; %i < 2 ; %i++ )
	{
		if ( %this.pd[ %i ] < 0 )
		{
			%this.pd[ %i ] = 0;
		}

		if ( %this.pd[ %i ] >= %this.height - 7)
		{
			%this.pd[ %i ] = %this.height - 7;
		}
	}

	// main pong code (well, not really "main")
	if ( !%this.movePong() )
	{
		return;
	}

	// draw frame
	%this.drawPong();
	%this.drawPaddle( 0 );
	%this.drawPaddle( 1 );
	%this.drawScore( 0 );
	%this.drawScore( 1 );

	// set up next frame
	%this.pt = %this.schedule( 1000 / 15, "pt" );
}