The cipher used to encrypt the riddle is a mixture of several different
Caesar ciphers. Specifically, we shift the six lines of the encrypted text back by 1, 2, 3, 4, 4, 5 places respectively
to get the following riddle:
Look carefully and you will find
An ant forms in a digital world
Walking across the page
The image assigned, collided,
Fired by a gun. Here after r.
But what am I?
Inspired by @GarethMcCaughan's answer, the solution to this could be
a glider in a cellular automaton. Quoting from Wikipedia (emphasis mine):
"The glider is a pattern that travels across the board in Conway's Game of Life. It was first discovered by Richard K. Guy in 1970, while John Conway's group was attempting to track the evolution of the R-pentomino. [...] John Conway has remarked that he wishes he hadn't called it the glider. The game was developed before computers and after seeing it animated, he feels the glider looks more like an ant walking across the plane. [...] Gliders are important to the Game of Life because they are easily produced, can be collided with each other to form more complicated objects, and can be used to transmit information over long distances. For instance, eight gliders can be positioned so that they collide to form a Gosper glider gun."
So gliders can be seen as ants walking across a page; they exist in a digital world; they form images and collide with each other; they are fired by guns and were discovered after the R-pentomino.