Great take on the theme. I did find movement a bit awkward though, maybe if the default falling motion was a bit faster?
It's a shame the web version doesn't work but its good you had a downloadable version. Others have already mentioned the compression format, but you can also try going to "Build Settings" > "Player settings" > "Other Settings" and turn off "Strip Engine Code", set "Managed Stripping Level" to low, set "Vertex Compression" to None, and turn off "Optimize Mesh Data".