20 Apr 2019

Biojet gameplay - A new Amiga PD game

Another one new release for the Amiga.
This time paranoicb tests on his Vampire600 a new game called Biojet.
Its a game made by Roy Schneider. This game was released on Aminet today.
Written in ASM 68k this game offers parallax scrolling fast paced 50hz gameplay and a really
nice music and graphics. On the video below you will see some gameplay footage.


In 1997 a game released was called 'Cybergene' for the MS-DOS platform.
The graphics for that project had been drawn on several AMIGA's. The Author always
wanted to use the graphics again for an AMIGA platformer. Well the result
is a bit different and it is 22 years late - but finally...

Technical Info:

The game is entirely written in 68K assembly, taking advantage of horizontal
sprite multiplexing, using a heavy copperlist, in order to make the scrolling
background image. To generate that 'stone' background image, sprite stripes
are used, 16 pixels wide and 192 pixels high. Sprite 4 is placed at x=0,y=0
and sprite 5 is placed x=16,y=0. The sprite priority register is set, so that
sprites appear beyond the playfield bitmap data. When the raster beam reaches
the sprite 5 on the first line, the sprite control register for sprite 4 is
changed x-wise by 32 pixels, making the chipset repeating the pixel line of
sprite 4 right to sprite 5. Then when the raster beam has reached that
'multiplexed' line, the control register for sprite 5 is changed, so that this
sprite is repeated right to the already repeated sprite 4. This is now repeated
until the scanline ends.
To put it into a nutshell, the copper is 'running' ahead of the beam, twisting
the sprite registers. On the end of each scanline the sprite positions are
turned back to normal and the procedure is now repeated for the next and next
scanline, until we reach the bottom line of the playfield. The slow scrolling
effect is made simply by changing the sprite images for the two sprites. The
foreground graphics is a standard 4-plane playfield giving 16 colors using a 352
pixel wide screen with a modulo of 4, ending up with 320 logical pixels per
scanline. For scrolling purposes 16 pixels are hidden on the left, by setting up
the window accordingly. So we end up with 304 visible pixels per scanline. The
game character is build up from two 16-color sprites made from four 4-color
sprites 0/1/2/3.
Sprite 6-7 stay unused. The bottom drop graphics is 5 planes, filling up the
screen to scan line 245. So on NTSC machines some of the credits might not be
visible, but that does not effect the game play.


- Any AMIGA with 68k CPU.
- 512 KB Chip and 512 KB (Slow)Fast or more.
- OCS/ECS/AGA chipset, PAL/NTSC supported.
- Kickstart 1.2 or higher

The game runs under Kickstart 1.2, 1.3, 2.0, 3.0 and
3.1 on OCS, ECS and AGA computers.

More info and download link below:

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