BATS
----
Here's a batty program for your 16K Spectrum from Colin Gooch of Ilminster.

In this program, you are a bat flying about trying to secure some moths for
your supper. Movement is made via the four "arrow" keys on the Spectrum, and
to make a catch you have to place the centre of the bat character directly
over the moth. Watch out though - the moth moves totally at random.

Because your bat cannot fly in bright light, the moth can escape you by
flying into the lighted window in the top left-hand corner of the screen. All
you have to do is trap the moth before it gets there! The game ends when you
have attempted to catch ten moths, although there is a bonus if you manage to
catch all ten.

Holy bat-catcher!

Initialisation of the graphics is done in lines 2230 and 2250. This leads
straight into the instruction page which is completed by lines 2300 to 3030.
This last section is not repeated when you play subsequent games after your
first.

The main program begins with line 50, which calls the subroutine to print the
screen display, followed by lines 90 to 120 which initialise the screen
co-ordinates for the bat and the moth. Lines 200 to 300 are a loop which
constantly moves the position of the moth, and if the right keys are pressed
this section of the program actually moves the bat.

The conditional statements for the moth make sure that it stays within the
screen area and also reverse its direction should it get too near to the
edge. The moth is moved 'dx' and 'dy' across and up the screen, but it is not
incremented on each pass of the loop. It is the RND value in lines 230 and
240 which look after this latter task, and it is this which gives the moth
its random movement.

The conditional statements for the bat read the keyboard, keep the bat on the
screen and also ensure that it will not move into the area of the window.
Line 320 detects a caught moth and moves on to the scoring section of the
program. Lines 330 to 350 detect the moth in the vicinity of the window, and
once there it is automatically drawn into the window, the moth's home score
is updated and a new moth appears down in the bottom right-hand are of the
screen.

Scoring is carried out from lines 370 and 520. This includes a "high score"
routine, and offers you a bonus "go" if you managed to catch ten moths out of
ten. This invitation comes courtesy of lines 530 to 580.

Flying tonight

The REM at line 20 indicates which lines need letters typed in the graphics
mode. Lines 250 and 260 use keyboard graphics and it is important that you
get four blanks at the end of each string.

Line 3400 looks the most complicated. However, if you decide that you don't
want to put a title or instructions in your listing, you could always rewrite
line 2400 to read:

2400 RETURN

and omit all from thereon.