Help needed: Decompressing old game files (.PES format))

I'm working on reverse-engineering an old MS-DOS game from 1989, The Playroom, and trying to analyze a specific file type. The files with the .PES extension seem to contain compressed assets (such as sprites and animations), but I haven't been able to extract them. I'm stuck identifying the compression method used and hoping someone can point me in the right direction!

What I Know So Far:

• The game was released in 1989 and runs on an unknown engine.
• The files have the .PES extension and seem to contain graphical elements.
• A hex dump reveals a consistent header structure, but the exact encoding or compression remains unclear.

What I've Tried:

• Attempted to open the file using common decompression tools—without success.
• Researched similar retro game formats, but found no clear matches.
• Analyzed the structure to identify patterns or markers.

My Question: Does anyone have experience with this type of compression format or know how I can analyze it further? Any suggestions are welcome—whether it's a tool I haven't tried yet, a similar case, or a method to decode the header.

Thanks in advance for your help!

PS: I've developed a small tool that generates a hex dump and verifies whether .PES files match the known structure. You can download it here:https://github.com/PeterSwinkels/ThePlayroomPESFileViewer