Ahh, that would be because they are in the "hidden" category. You can still install them by apt-get, provided you know the package name. You can try apt-get instalľ angry*. It will ask you before it starts installing.
Really? That's interesting, thanks! I remember being able to install both gas balls and angry birds via HAM back in the day, but this time around neither of them were visible, and I even think I tried apt-get install as well with gas balls. I'll try with angry birds later using the procedure you recommend and I'll let you know if it works.