Defender (Tandy MC10) by Jim Gerrie

DEFENDER - PUR 80

You'll notice in line 8 the GOTO has no line number.  I'm taking advantage of the fact that if no line number is provided then Basic assumes line 0, which is the line I want it to go to.  This keeps me under the 72 character limit.

Lines 1-3 are the ASCII characters in strings for the city.  These characters are from the different block characters in the Motorola MC6847 character set, values 128-255.

Line 0 sets random starting points for the incoming missiles.

Lines 4-5 peek the keyboard input buffer so I can get continuous input in 8 directions using the AWSZ keys.  If you hold down two at a time, you can get diagonal motion.

Key Input:

    AW      W      WS
     \      |     /
      A     +    W
      /     |     \ 
    AZ      Z      SZ

Lines 6-9 move the targeting cursor and the missiles.  Line 9 also has the restart instructions for the end of the game.