Drag with the mouse to scroll the playfield around. The cloud is actually a sprite. If you click on it, "HIT" will be displayed for a short period.
In this applet there are 5 different threads. Two for the vulture animations, one for the walking man, one for rasterizing these images on the playfield and one for painting the playfield on the screen. Since we have all these threads, there is lots of work going on in the background, and this requires a good amount of resources. If you have a slow computer, the animation will be slow. I recommend a high end PIII processor. If it is still slow, run the applet from commandline by typing:
appletviewer http://www.ai.mit.edu/~mtsezgin/6.837/PS01/index.html
Netscape sometimes halts since its garbage collecter doesn't work properly.
Here is the source code.
Credits: The images are taken from the game Dark Castle by Delta Tao software.