busyloop/lolcat — reverse-engineered prompt

Build me a small Ruby command line tool that makes terminal output rainbow colored. I want to be able to pipe text into it, or pass it text files, and have it print the same words back with smooth shifting colors, like a fun version of cat.

It should work nicely in a normal terminal, keep line breaks and spacing, and not mess up plain text besides adding color. Include a simple executable command, a small library file so the color logic is reusable, basic help text, and a short manual or README showing how to install and use it on Linux and Mac.

Please keep it lightweight, with sensible defaults, and make sure common examples like echo hello into lolcat and lolcat somefile.txt work. If you need exact terminal color code details, look up current docs online and use the current best practice.