Aditya Ravi Shankar built the clone in an attempt to improve his coding skills. He set himself a month to rebuild the game in the browser, chopping through the original game's files to get sprites, sounds and specs exactly right.
"In hindsight, I might have wanted to take smaller steps and make a tower defense game instead of jumping directly into an RTS," says Shankar, in a post about the game's development on his blog. "Trying to do the whole thing in under a month all by myself wasn't the smartest idea."
Shankar's recreation of the game includes buildings, terrain, combat, tiberium harvesting and regrowth, and the ability to sell and repair buildings. It has fog of war, too, a pannable map, different cursors, tooltips, and drag selection for multiple units. For the time being, however, it's limited to just a few buildings and units, a very small map, and the occasional glitch -- a few of our tanks got stuck in the sea during testing.
Shankar admits: "The project is far from complete and there is still some polishing up to do," but nonetheless it's an extraordinary achievement. It can be played here (it works best in Chrome or Firefox). If you're curious, you can check out the source code too, here.