Simplify the following text for a Grade 10 native English-speaking person.
Original: In its prototype stage , the Atari 5200 was originally called the `` Atari Video System X - Advanced Video Computer System '' , and was codenamed `` Pam '' after a female employee at Atari Inc. .
Simplified: While it was being designed , the Atari 5200 called the `` Atari Video System X - Advanced Video Computer System . '' Atari protected the design with a codename , `` Pam , '' after a female employee at Atari .