# ALIEN 3 AI by DEVILSYSTEM (Markus Hohmann)

**URL:** <https://forum.cpcwiki.eu/t/alien-3-ia-de-devilsystem-markus-hohmann/842>\
**Category:** AI remakes\
**Tags:** gx4000, cpcplus\
**Created:** [October 14, 2026, 9:50am UTC](https://forum.cpcwiki.eu/t/alien-3-ia-de-devilsystem-markus-hohmann/842 "2026-10-14T09:50:13Z")\
**Posts on this page:** 1\
**Page:** 2

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**Author:** ![lightforce6128](https://forum.cpcwiki.eu/user_avatar/forum.cpcwiki.eu/lightforce6128/32/32_2.png) [@lightforce6128](https://forum.cpcwiki.eu/u/lightforce6128)\
**Post date:** [October 16, 2026, 5:35pm UTC](https://forum.cpcwiki.eu/t/alien-3-ia-de-devilsystem-markus-hohmann/842/23 "2026-10-16T17:35:21Z")

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I didn’t use a disassembler, so I have to guess:

The left-to-right scrolling uses CRTC registers 12 and 13 (four-pixel jumps in Mode 0). By splitting the movement across two buffers, the jumps are reduced to two pixels.

The top-to-bottom scrolling uses CRTC register 5 to split an 8-pixel line between the main screen and an auxiliary screen. This would allow scrolling in 1-pixel steps, but for the sake of symmetry, it scrolls by 2 pixels.

The explanation above can probably be mostly disregarded, considering that the demo runs in overscan.

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