Sentinels of Ceth is a shoot 'em up in which the player must protect

Sentinels of Ceth is a shoot 'em up in which the player must protect
twelve gems placed in the middle of the screen from being stolen by
enemy ships.

After each attack wave the player can purchase upgrades for the
defense ship and ammunition for special weapons. Each attack wave
becomes longer and harder than the one before, adding more enemies as
well as new ones. Stolen gems are lost forever, but as long as there
is at least one on screen, the game continues, regardless of how many
times the player's ship is destroyed. Once all gems have been stolen
the game is over.

Download 1 is version 1.5, and includes a registration code
Download 2 is 1.2
Download 3 is 1.0

After Stick Man Games folded, a company called Monkey Byte re-released
this game as Sentinels of Ceth 2.0. This version dropped support for
System 7.

Compatibility
Architecture: PPC

Minimum system requirements:

* PowerPC 601 processor at 60 MHz
* Mac OS 7.5.3
* QuickTime 2.5
* 6 MB of free RAM
* 6.5 MB of free disk space
* A monitor capable of displaying thousands of colors