Yay, falling rocks!
Progress has been going incredibly slowly, not helped by my getting distracted a lot. Anyway, as can be seen below (well, I could have faked it, but if I had you’d be seeing this post much earlier) pressing space fires bullets randomly from the centre, and when they collide with the cave wall, cause a rock to fall. Finally!

Hurrah, falling rocks.
So, no dinosaurs, no player, and the rocks fall through the floor. Gah! Why are so many other people so far ahead? It’s demoralising… Though admittedly I haven’t spent that long on it, I guess.
I might as well take this opportunity to explain what I’m using for this: C++ with SDL, in the Code::Blocks IDE. GIMP for the graphics… and that’s about it. 
Comments
29. Aug 2009 · 18:42 UTC
Looks nice. 

AtkinsSJ
29. Aug 2009 · 19:20 UTC
Thanks! I’ve just managed to get the rocks not to fall through things. 😀