Good point, I actually considered Javascript too. Though it seems like there's no one-size-fits-all tool, but right tools for right problems. I'd use Javascript for in-browser games, but something different for standalone ones if high portability is the requirement. Lua seems to be a good choice, because it's de-facto industry standard in gamedev and runs on anything but my door bell (
http://luajit.org/luajit.html). So my current best idea is to write all control logic in Lua, and platform-specific low-level stuff in C++. Regarding the speed concerns, both Javascript and Lua have JIT, and anyways, no Lua or C++ code should be visible in the profiler at all if we're talking about performance. It seems to me most computations should be done on GPU instead.