You can play levels you made in this game.
Use free software
to make levels.
A screen-shot making a level
1. Download software
Go to the page of Tiled (Level Editor)
2. Download a level format and a sample data
How to Make a Level [pdf]
How to set up a data for Tiled, how to play with your levels.
This is a sample level data for a reference for settings.
I recommend you to read "How to Make a Level" with this sample data.
3. Make your levels by modifying a template data
This is the level data with necessary settings.
Make a new level by modifying this data.