Some notes about the old BBC Micro repton format

schermo: 10x6 sprite
sprite: 16x32 pixel
mappa: 28x24 sprite

richiede schermo 160x192

schermo BBC (modo 5): 160x256 pixel
schermo PC (modo 13): 320x200 pixel

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Jasper Renow-Clarke notes:
http://sol.soc.staffs.ac.uk/cm4bcjs/David/S3/Jasper/repton
cm5hdjjr@bs41.staffs.ac.uk

here are the locations of all the stuff

Offset  Contents
0 - 63   Passwords
64 - 79  Time limits
80 - 95  Editor codes
96 - 223 Transporter destinations
224 - 255 Colour Palette
256 - 3615 Maps
3616 - 9760 Sprites

The passwords are stored in 8 bit form
and if you use this formular the passwords come out
char = password_byte XOR (64-(file_offset+1))

The time limits are stored in word format

The editor codes are also in word format
however if the editor codes are all 0's it
indicates a home-made level

The transporter destinations are stored as follows

 A1  A2  A3  A4  B1  B2  B3 ... H4
xyxyxyxyxyxyxyxyxyxyxyxyxyxy   xyxy

Source (x,y) first then Destination (x,y)

The Colour Palette is stored using bytes to
represent each colour (0..4)

The following table shows the colour mappings

0 - Black         4 - Light blue
1 - Light red     5 - Light magenta
2 - Light green   6 - Light cyan
3 - Yellow        7 - White

The maps are stored in 5 bit form
e.g.

1  0  1  1  0  0  1  1  0  1  0  0  1  1  1  0  1  0  1  1  1  0  1  1  0  1
4  2  1  16 8  4  2  1  1  16 8  4  2  1  16 8  4  2  1  16 8  4  2  2  1
-------  -------------  -  -------------  -------------  ----------  ----
   2           1        4        3              2            5          4  7

Stored sequentially from top,left to bottom,right

Values in the range 0->31

A map is 28x24 in size

There are 8 maps A -> H

The sprites
-----------

Each sprite is 128 bytes long

There are 48 sprites

The sprite size is 16x32

They are stored in 2 bit form

ah  bh  ch  dh  al  bl  cl  dl
   high bits       low bits

Pixel colour = Palette_entry(ah*2)+al e.t.c

Four pixels per byte