That is a lot of transformation for a system that was not main stream and did not sell on a wide scale. Compared to the main stream portables, it had a very small fan base. The definition of the terms above are as follows;
NLU= non lit unit, the screen did not have any light
FLU=front lit unit, the screen had a front light
BLU=back lit unit, the screen had a backlight
BLU+=back lit unit, it had a totally different type of LCD, some say it was the best screen the unit had.
     All of the different models are identical. If you lined them all up there is no way of telling them apart. They used the same outward casing for every model and they are all white and gray in color. This sparked a lot of modifying of the units by their respective owners by painting.
     The proprietary operating system on the NLU and the FLU was the same. Note that when you started up the old filmware you were greeted by a yellow, orange, and pink GUI. That is the best I can remember of it. (I changed the filmware on my NLU to the BLU filmware by flashing the unit.) Recognizing a community of Homebrew programmers existed, GamePark did something unique with their portable, they decided to allow homebrew applications to be ran on their gaming machine. When you registered your system on their website, you could download a small file, called "Free Launcher," that allowed you to launch or boot a  non commercial program. The file, or program, was especially encoded to your unit's serial number, meaning you couldn't copy it and pass it along to someone else. Without this launcher on the NLU and the FLU, that contained the original older filmware, you could not play any homebrew programs and you couldn't flash a different filmware to your unit! The unit used Smart Media Cards for games, this is where the Free Launcher resided. (The GP32 uses the Smart Media card like a computer would use a hard drive.) GamePark quit offering the Free Launcher after they quit manufacturing the unit with the old filmware. This little thing about the Free launcher has caused misery to some who have read a little about the GP32, and unknowingly purchased a NLU or FLU from ebay, only to find out later about the complications of running any homebrew without it.
     With the BLU and BLU+ units you were greeted with a white and blue color GUI and the "Free Launcher" program was built into the new filmware. The menu system of both, the old and new filmware, are very simple and easy to negotiate.
     The unit came with a cable that enabled you to hook it to your computer through the USB port. Loading a separate program on your computer called a "GP32 Manager" enabled you to place and load homebrewed games and programs onto your GP32's blank Smart Media card. It also had the feature of installing programs, formating, and setting up a file system that the GP32 recognized on your SMC. All file names have a limit of eight letters and will be rejected unless you change the name to fit within that requirement. The GP32 Manager is a free download or is included on a CD that comes with the BLU and BLU+.
     The GP32 was launched into the market at the same time that Nintendo's Original Non-lit GBA was the darling of the portable gaming world. The GP32 was never marketed in the US. One must understand that the GP32 is a much more powerful system than the GBA. In comparison, the GP32 was more like a small portable gaming computer. At one time it was the most powerful portable on the market having a 133 MHz ARM CPU and 8 megs of on-board  ram compared to GBA's 16 MHz ARM CPU.
     The quality build of the unit is debatable. The outward housing is of a very good thick plastic, not the thin cheap plastic usually found on Chinese systems. Many have taken them apart and modded their cases, some turned out looking really sharp. There have been reports where the speakers were hooked up backwards, opening them up and a quick soldering job fixed this issue . Others never really liked the joy stick, it is a bit wiggly and clicky with a loose feel. Many craved a traditional cross shaped directional button. The BLU and The BLU+ were the final incarnation of the system and really the best models to own and gave the best overall performance.

     All of the commercial games have very amazingly highly detailed graphics, showing off the systems capabilities. I'm talking of PS1 quality here. There are some games that are worth chasing down and finding, one of them is Blue Angelo which was a long awaited title for the system. A side scrolling action game. Others that are note worthy are Her Knights,  Astonishia Story (the only RPG the system has and it is in the Korean language, PS1 graphics and animation), Dungeon & Guarder, Little Wizard, Kimchi-men, GP Fight, Pinball Dreams, Raphael (port of Castle Excellent), and Tomak: Save the Earth Again (the only shumup for the system). I am not saying that maybe some of the other games you might not find entertaining, I am just listing the cream of the crop. At the moment, the commercial games are rare and very hard to find and remember they are in Korean, no English.
     Unlike commercial portable gaming systems that use proprietary carts to load their games on, GamePark decided to use writable Smart Media Cards, or SMC, for their games. The same kind that was used in Digital cameras. The medium no longer is being made or used, this causes it to be very expensive to acquire. The GP32 is also limited as to how large of a SMC it can recognize and read, with it being limited to 128 megs. This doesn't limit you as bad as you might think, unless you like big files. The link cable enables you to hook the GP32 up to your computer so that you can transfer files to the SMC. But I would highly recommend a card reader. The transfer rate is a great deal better and you won't end up running your batteries down. It takes a lot of energy to do the transfer directly to the SMC while in the GP32. Plus getting your computer to recognize your GP32 can be troublesome.
    Most people did not purchase the system to play the commercial games, but to use emulators to play  games from retro console gaming systems. The emulators are a result of  Homebrew programmers (very highly skilled programmers) getting a hold of the system and utilizing the ability of being able to write and run homebrew. There are emulators for pretty much all of the old classic computers and gaming machines. Be warned, unless you have had some experience, setting up an emulator requires some technical skills and patience. There is the issue of game compatibility as with all emulators, some games work, some games have issues and some games do not work. There is also the issue of the legality of obtaining game roms and using them in this fashion. There was a keyboard made available that could be hooked into the bottom of the unit making it ideal for those emulators of older retro computers, but it is rare and hard to find. You also need the ability to read "read me" files and the patience to wade knee deep into old forum posts to solve some of the problems you may run into.
     There is also a treasure trove of wonderful ports and homebrewed games for this system reaching into the hundreds in number and they are free to download.  I like shumups so Bolcataxian stays on one of my SMC. There is Beats of Rage, a Streets of Rage sequel, great game. Columns has been ported. There is the strategy game GP32WAR similar to Advance Wars on the GBA. Giana's Return is ported, plays similar to Super Mario Bros. Most of the homebrew games fall into the puzzle, early arcade, and shumups category. One of the great things about this system is, if you are a " Homebrew, or a want to be, programmer" then you can try your skills out and see the results, even sharing them with a community. Though many have long since moved on to the GP2X, there are still those that cling to the GP32 and would certainly appreciate anything well programed. Remember that Homebrew games may require the same skills to set up as the emulators.