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Impossible City

impossible hardware effects ideosyncracies display artifacts real Atari real hardware only double true

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Posted Wed Mar 16, 2016 8:56 AM

Impossible City


Throw the BW switch on your Atari and watch the buildings turn impossibly phat and crooked; throw the switch again and you've got a dreamy hypnotic display with a whole bunch of other impossible effects.


Download the game here:



StarBlitz Plasma artifacting at 30 FPS.JPG

This thread is to explore and discuss these interesting real-hardware-only effects and game ideas for using them, as well as the other effects present in the game that can only be experienced with a real Atari.


Directions: To experience the controversial StarBlitz effects simply play in a darkened room lit only by the CRT using an NTSC Atari, PAL is not supported. Background music will enhance the effects noticeably and differently in both modes.


Both modes are fun to play and it's interesting to switch between them; just like real life, the City can look impossibly phat and crooked without rose colored glasses ;)
The buildings are built of solid tile pixels which are two pixels wide, and solid - they become phatter when the BW switch activates 60 HZ. They also change shading, and it is possible to see single playfield pixels within the designs on the buildings.

While a crooked City is revealed by design, it renders with a subpixel never actually used in the game.   


Stepping through the frames in Stella will show there are no 3 pixel multicolored buildings, and that the City is crooked by a full tile pixel.


The bitplane has multiplied too which is yet another new type of artifacting, and the software RAM doubler has become a RAM tripler; StarBlitz graphical virtual worlds are stored as bitmaps in high RAM and get expanded 2:1 to phat pixels on the fly by the RAM doubler. This ideosyncracy in the analog signal causes the the bitmaps to be expanded 3:1 instead and increases the bitplane with no additional overhead and thus no synaptic seepage:


StarBlitz does not cause synaptic seepage, not even when overloading the RAM doubler.


Also tagged with one or more of these keywords: impossible hardware effects, ideosyncracies, display artifacts, real Atari, real hardware only, double true

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