This download includes the client for Linux. just unzip it and doubleclick the *.sh-File.if you now how to open jar files on windows/mac you can run it there too. The control is simple: WASD or the Arrow-keys control a little orb. scroll up or down to move the orb away or to you. Click left mouse button to Spawn new orbs. Press right mouse button and hold it to look around. Press "tabulator" to see more commands.
Works, but laggs on my laptop when creating planets.