Nice - I'm always interested in HTML5 stuff
I don't know what the difference is between "active rendering" and "passive drawing", but I get the impression something like this would be easier to do with plain old-fashioned html - just display the board in a <table> element instead of using a <canvas>.
This is probably just an experiment though, so fair enough
I used the term 'passive' as opposite from 'active'. Active rendering is rendering your frame each cycle to maintain a constant fps like 30 or 60. Passive rendering is that I only render a frame when it's needed. In this case on a click/touch because that's when sometimes changes in the screen. It should save some power and give some extra performance.
But you're right about plain old html, I could even use svg elements for the objects.
It's just that I am used to writing a game, trying to render each frame while maintaining 60 fps. But that isn't necessarily needed or the best way to program something.
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Jenswa 
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