Patch:Tantalus ray

The Tantalus ray is a sprite in Keen 2 and the main focus of them game. Keen must destroy eight rays, each pointed at a major Earth city to win the game. While a sprite, the Tantalus behaves more like a machine or a construct of tiles. Related patches are Patch:Earth Explodes

How the tantalus works

The tantalus ray is in essence a sprite. It appears as a small purple spark by default, and it is this Keen must shoot to destroy the ray. The presence of this sprite affects a number of tiles, most notably when the tantalus is shot.

Keen can interact with the tantalus in two ways, by flipping its switch, which causes the tantalus to detonate, and by shooting the tantalus, which destroys it and saves a city. This page is divided into several sections, the sprite properties of the tantalus, the destruction sequence of the tantalus (when Keen shoots it) and miscellaneous patches. Patches involving the destruction of earth are located at Patch:Earth Explodes

Tantalus ray sprite

These patches relate to the Tantalus ray as a sprite, mostly the purple spark that Keen must shoot to destroy the ray. By itself this is not a particularly exciting sprite, but interesting things can be made to happen when it is patched.

Sprite Type

Tantalus rays are type 8, which doesn't really do anything by default. There is also the property of the zap\zot sprites produced when the Tantalus is destroyed, type 13, which also doesn't do much. (Thought it may be useful for complex patching.)

#Yorp sprite type:
%patch $3DE7 $08 
#Tantalus
%patch $4807 $0D 
#Tantalus destroyed zaps

Sprite Behavior

The Tantalus ray's default behavior is to sit, animate and wait for Keen to shoot it. This behavior never changes. The Tantalus ray collision is the most complex in the game and thus has its own section.

Behaviors:
$46DFW Sit and animate
$4716W Tantalus ray collision

%patch $3E0A $46DFW

%patch $3E0F $4716W 
#Tantalus ray collision

Animations

%patch $3E14 $0080W 
#Start

%patch $46F0 $0080W 
#Sprite
%patch $46ED $0003W 
#Frames used -1

Sounds

This is the sound made when the Tantalus is shot and tiles are being replaced.

%patch $47F3 $25 
#Sound of tiles being replaced

#Don't make sounds:
%patch $47F6 $90 $90 $90

Sprite Collision

The sequence of events that occur when the Tantalus is shot by Keen is one of the most complex sprite collisions in Keen Vorticons. It involves multiple tile replacements in a series of steps that give the impression the machine is blowing up.

TODO

Replace all the Tantalus tiles at instantly

This patch stops the regular, orderly replacement (explosion) of Tantalus tiles and simply replaces everything as soon as the Tantalus is shot. It may be slightly unstable as a patch.

#Replace all the Tantalus stuff at once
%patch $486A $08