FireLink

The fire effect is one of the most iconic demoscene tricks — every demo on the Amiga, Atari ST or PC had one. The algorithm is beautifully simple: seed random hot pixels at the bottom of the screen, then propagate upward by averaging each pixel with its neighbors below and subtracting a small cooling factor. The result is a surprisingly realistic flame that rises, flickers and fades — all from a few lines of integer math and a color palette lookup.

FireLink wraps this classic effect into a clickable banner applet. A transparent foreground image (the link text or logo) floats over the flames, with an optional second image for mouseover state. The three-color gradient (backColor → midColor → endColor) lets you create anything from traditional red/yellow fire to white smoke, green plasma or blue ice. The cool parameter controls flame height, and with mouse enabled you can paint fire with the cursor.

Originally a Java applet (1997). The JavaScript/Canvas port uses the same fire algorithm but renders into an HTML5 <canvas> via ImageData. Overlay images are loaded as standard <img> elements and composited per-pixel with alpha blending.

Features

Real-time fire simulation with neighbor-averaging diffusion
Transparent foreground image overlay (GIF/PNG)
Mouseover image swap
Fully customizable three-color gradient
Adjustable flame height, spot density and clearing rate
Mouse/touch-as-torch interaction

Applet Parameters

Name	Type	Description	Default
`image`	filename	Transparent foreground image (GIF) shown over the fire	–
`image2`	filename	Alternative image shown on mouseover	–
`cool`	int (0–16)	Cooling factor — higher values produce shorter flames	1
`spots`	int	Number of new fire hotspots seeded at the bottom each frame	width/16
`clears`	int	Number of bottom pixels cleared each frame	width/8
`mouse`	–	Enable mouse-as-torch (presence enables it)	off
`backColor`	hex color	Color gradient start (coldest)	#000000
`midColor`	hex color	Color gradient midpoint	#FF0000
`endColor`	hex color	Color gradient end (hottest)	#00FFFF

Parameters (FIRELINK_CFG)

Name	Type	Description	Default
`cool`	int	Cooling factor 0–16 (higher = shorter flames)	`1`
`spots`	int	Hot spots seeded per frame	`width/16`
`clears`	int	Spots cleared per frame	`width/8`
`mouse`	boolean	Enable mouse/touch-as-torch	`false`
`backColor`	string	Gradient start hex color	`"#000000"`
`midColor`	string	Gradient midpoint hex color	`"#FF0000"`
`endColor`	string	Gradient end hex color	`"#00FFFF"`

Applet Code Example

<applet archive="FireLink.jar"
  code="FireLink.class" width="100" height="30">
  <param name="link" value="https://www.chriscohnen.de">
  <param name="image" value="hotlink.gif">
  <param name="cool" value="2">
  <param name="spots" value="20">
  <param name="clears" value="10">
  <param name="backColor" value="#000000">
  <param name="midColor" value="#FF0000">
  <param name="endColor" value="#FFFF66">
</applet>

JavaScript Canvas Version

<canvas id="game" width="200" height="60"></canvas>
<img id="overlay" src="hotlink.gif" style="display:none">
<script>var FIRELINK_CFG = { cool: 2, spots: 20, mouse: true };</script>
<script src="firelink.min.js"></script>

Version History

Version	Date	Changes
2.1	May 1997	First public version — link image with background fire
3.0	November 1999	Mouseover image, target window, renamed “pic” to “image”
3.2	November 2003	Build system, obfuscation
3.3	August 2004	Fixed left mouse click to link