A few days ago, Valve released a new beta version of Portal, which includes Linux support. This is the latest step to date towards their goal (to my knowledge) of porting all of their games to Linux. Since I use Linux almost exclusively, this marked a good excuse for me to finally get – and play – Portal.
Optimus basically consists of two GPUs, an integrated one (in my case from Intel), and a more powerful "discrete" one. The integrated one is the one which talks to the display, and it takes some work from the drivers and the operating system to render things on the powerful GPU, and then display it through the integrated GPU.
Now at the time I'm writing this, Optimus is still not officially supported on Linux systems. At best, officially, you can use the more powerful GPU to perform calculations, but not display any of them. However, the Bumblebee project provides wrapper scripts that cause programs called from them to render on the faster GPU, and then shovels the images to the discrite GPU behind their back. The currently favored script is primusrun from Primus, which is now bundled with Bumblebee.
I first tried starting Portal with the integrated graphics. The performance was sufficient (thanks Valve and Intel for working on this!), but I did notice some odd glitches, where some transparent objects ignored the z buffer (meaning they were painted in front of the walls they were actually behind).
Then I tried telling Steam to start Portal with primusrun, and it worked perfectly! Not a single glitch or lock-up. And this from a game that's still in beta.
The game is awesomly fun, if a bit short. Well, short if you only play it once, which I most certainly will not. Oh, by the way, don't head for the options, notice some "funneling" option in which "the computer helps you aim for floor portals", interpret it as some kind of auto-aiming, think you're "too hardcore" for that, and disable it. It helps your character land on portals in free fall. I'm glad I found and reabled it at about map 16 or so. I'm definitely trying more tricks now that it's on.
At the same time, I started thinking that with a bit of mapping, this would make an ideal game for small children. If you take out any dangerous environments, turrets and energy balls, you get a perfectly non-violent First Person "Shooter". If you craft the maps so that you can't ever get stuck, you also get a very frustration-free experience.
You'd have to start the tutorials really, really slow. The original tutorials are already nice and easy, but they still expect the player to know about WASD movement and mouse look. For absolute gaming novices, you can't assume that. The first levels would have no portals at all, and just require you to walk to the exit. Say a flat two-room maze for the first level, stairs in the second, and a jumping obstacle in the third. And they will still spend half an hour there, because once you discover the space bar, your afternoon is booked at that age.
Then the portals would be introduced, without player interaction at first. One puzzle with portals in the walls, another where they are in the floor and/or ceiling. Then the portal gun, one color for several maps. Start with a map where there's only one place you can even place the portal. Then only one wall, then maybe more. Then, when the second color is introduced (whith repeated voice instructions), have a map where there are exactly two places you can place portals.
Finally, a largish map with all-white walls, for maximal portalling fun. In fact, you can stop making maps there, because once kids hit this one, there will be no reason to progress, ever. You don't even need a win condition. For a child, an all-portal map would be the win condition.