Donald Osselaer published three versions ofthe Fermium puzzle. The first one, published on Puzzle will be played and manufactured by Maurice Vigouroux, is level 100, and needs some extra colour marks on the central pieces for the solution to be unique.
Two improvements were published in Puzzle World. The first one forces the use of a rotational move and increases the level to 105 or 108, depending on the way the moves are counted. The second one gets rid of the need for colour marks in addition to the three basic colours.
"I am very glad ... in fact I am ecstatic ... that it works 'completely' as intended! This means that it uses 100 logical human moves to free the first piece, which comes out in the same rotating fashion as with the Xenon."
"For newcomers to this type of puzzles I do not advise to start with the Fermium. Start with Natrium, then move up to Frans de Vreugd's Torture ... once you know that one and can disassemble and assemble it without the solution you're probably ready for the Xenon and once you know your way around the Xenon you can try my new Fermium as the basic principles of the last two are not entirely but quite the same." -Donald Osselaer