CusAsm is an advanced development tool meant to be used by expert developers and reverse engineers. It works as a lightweight PRINCE.EXE assembler that is capable of detecting the bytes that need to be edited in each version of the game.
To start using it, you should read the forum information first. The input is a Turbo Assembler generated paste from any PRINCE.EXE file. The output will be the specifications to edit each PRINCE.EXE file in two formats: BBCode (ready to be pasted in the forum) and XML (ready to be included in the princed general hack library and therefore in CusPop).
This tool is very useful to create new hacks for the game and has been used to generate most of the options available in CusPop.