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So GridMaths.com is in open beta, now works reasonably well on iPad and recent desktop browsers.  Android browser support coming sometime soon.

Heres a pic my 9yo created while testing things out on the iPad.. with the obligatory battle scene [ dad vs browser quirks ? ] :

gridmaths_017_paul_dwg

Here’s a couple of sheets on how I like to present long multiplication…

Firstly a concrete rectangle where you can actually count the squares to satisfy yourself its right…

gridmaths_018

Then move to a more compact form, which still shows the rectangle grid, but not to scale..

gridmaths_019

This shows that lots of digits should not induce panic.. the same systematic approach works [ which is why computers can do multiplication so well ].

I think having the box grid is a nice way to remember where all the pieces come from [ single digit products ].  Also I think it really helps to use the blank grid spaces, rather than fill in every 0.

The lattice method is slightly more compact, but I think this box approach reminds students of whats really going on.

Thanks for all the emails and encouragement so far as I build this.

Enjoy, and let me know how your using GridMaths.

Xeno is a small demo project done over the weekend.  Click matching alien heiroglyphs to dissappear them.  Basic gameplay in HTML5 was pretty quick to prototype.

You can view it using Safari or Chrome browsers.  For iPhone, open in Safari and save to Home Screen, then you click the icon to load [for some reason fails to load directly, but works fine launched from Home Screen ]

For the path checking.. at first I did an exhaustive depth first search of all empty squares, but this exploded combinatorially.. so I used memoizing to reduce the repeat subpaths.. and then added a heuristic to find straight paths if they exist.  I probably should have looked up a decent path finding algorithm.  Sometimes its good to do things the blunt way yourself, so that you understand the problem and can then enjoy the beauty of a more elegant approach.

Hope you like the pictographs.. did them myself :]

Backstory

Lost in the dense Cambodian jungle you see what looks like an outcropping of ancient ruins.  Could that plynth be the entrance of an alien spacecraft which has lain dormant for thousands of years?  You wipe away the dust showing an irregular pattern of grooves.. you accidentally spill some water on the  console.

You hear a hiss followed by a gentle deep hum, and the panel under your palm begins to glow.   You must quickly match the glyphs to enter the Xeno’ ship…