If you are looking for the software itself to reference designs, note that is officially discontinued by Rovio.
Later updates (version 3.x) introduced "Space Eagles" as a consumable power-up, and the mobile version eventually added stamina meters and cosmetic microtransactions. PC users who dislike modern free-to-play practices often preserve version 2.1.0 as the definitive way to play. angry birds space 2.1.0 pc
The 2.1.0 update was the last version available for Windows. If you are looking for the software itself