Kindlet Dev SOS: Main class not found

I'd love to attempt to write a Picross kindlet, but I can't even get a basic "Hello World" to run. However I try to package it, I get a "Main class not found" error. What the heck am I doing wrong? Thanks in advance for your help.

FYI, I'm on a Paperwhite running 5.3.3.

Here is the current version of my kindlet: http://www.mediafire.com/download.php?dbvb7oxe1eddne0