If you want to see an example of this technology try this: http://bighead.poli.usp.br/~juca/code/svg/minigame/minigame.svg I will focus on the techniques I used to develop this game.
First thing you should do is to create the art in Inkscape. In my case, I have drawn the handheld console and all of the sprites that appear in the grey LCD display.
So, I select one sprite, paint it in soft grey, duplicate it with ctrl+D, paint the duplicated sprite in dark grey, set a value to its id attribute with ctrl+shift+O (let's suppose I give it id="my_light") then I group both copies of the sprite so that I can keep stuff organized and easily manageable. I repeat this procedure to all sprites that I have in my SVG.
<script xlink:href="myscript.js" />