Based on Black Hole, this aplet builds on the spiral drawing algorithm I put together. Instead of using screen pixels, this one uses an actual array and visualises each block of the array as the spiral iterates through it.

I thought it looked a bit more impressive then just drawing a big black hole on the screen. I also overcame the limits of the program usually stopping when a x,y value was generated that was out of range. There is a basic check to see that the value generated lies within the boundaries of the array, but it would continue to calculate positions until arrayWidth*1.5 and arrayHeight*1.5 so that the corners of the array were properly filled out. I'm not sure what the exact value would be, but its like trying to cram a square inside a circle - whats the minimum radius should the circle be?

I added a check that turns the array blue when the x,y values generated are completely out of range assuming that the all the array elements have been set/checked.