Rheolism is a Tetris like puzzle one line game written by Martin Hollis and David Moore with help from Olly Betts.
What is my point in listing this admittedly rather horrid looking program in a blog about programs as poetry, you might ask? Programming and poetry are both obsessed with limits. Consider the limerick. Like many poetic forms, it places specific limits on the number of lines which must usually rhyme and have a specific meter, with extra points given for internal rhymes, alliteration, and a surprise ending. Does this make it difficult to get your point across? Of course, it does, but it also makes it infinitely more satisfying to both compose and read.
In programming, if we do not set limits, then how will we know when we are done? How will the program be capable of running within the limits of our operating environment? Will it be fast enough, but not too fast? Will it keep to the limits of our program's specifications, whatever they may be?
A poem without limits is just prose, and a program without limits is crashed. As Albert Einstein said, "The difference between genius and stupidity is; genius has its limits."