The following tutorials present several Casper features in depth:
Title
Description
A counter on the Casper chain
Deploy a counter contract and call its entry points to increment it
ERC-20 implementation
Implement the ERC-20 standard for Casper
Key-value storage on Casper
Design a simple contract to store a value
Multi-signatures and key recovery
Learn to sign transactions with multiple keys
Smart contract upgrades
Learn how to upgrade smart contracts