28 Teletext control codes and MODE 7 128 To change the colour of the text 129 To make characters flash 129 To produce double-height characters 130 Graphics 132 Graphics codes 133 Making a large shape 133 Teletext graphics codes for the more adventurous 134 29 Advanced graphics 137 How to change the screen display modes 137 How to draw lines 138 How to draw a square in the centre of the screen 138 Changing the colour of the square 138 How to fill in with colour 138 How to change colours 139 How to plot a point on the screen 144 How to remove a point selectively 144 Animation 145 How to make a ball and move it on the screen 145 How to create your own ‘graphics’ characters 146 How to make a character (eg a man) 146 How to make him move 147 How to make a larger character 148 How to make the movement smoother 149 Making a complete lunar landing game 151 Running the program 154 The pitch envelope 158 The amplitude envelope 159 Note synchronisation and other effects 161 30 Sound 155 31 File handling 163 32 Speeding up programs and saving memory space168