Consider Greenfoot as a combination between a framework for creating two-dimensional grid assignments in Java and an integrated development environment (class browser, editor, compiler, execution, etc.) suitable for novice programmers. While Greenfoot supports the full Java language, it is especially useful for programming exercises that have a visual element. In Greenfoot, object visualization and object interaction are the key elements.
Open the TEXTBOOK here (use this as a guide and reference tool for the tutorials outlined below)
Greenfoot interface video introduction (Part one of two)
Greenfoot interface video introduction (Part two of two)
Resource guides
Tutorial 1 - Interacting with Greenfoot
Tutorial 2 - Movement and Key Control
Tutorial 3 - Detecting and Removing Actors and Making Methods
Tutorial 4 - Saving the World, Making and Playing Sound
Tutorial 5 - Adding a Randomly Moving Enemy
Tutorial 6 - How to Access One Object from Another
Now open up the textbook and work on augmenting the crab world you have created by completing or practicing the exercises from Chapter two to Chapter 4 (exercises outlined in blue boxes) .
For many more Greenfoot videos check out this YouTube channel
For many Greenfoot tips & tricks, check out this channel here