The C64 was not a huge success in France, with the Amstrad CPC the dominant 8-bit system. As a result, many French games which the C64 was more than capable of replicating were never released for it.
Sliders is one such example. It resembles Marble Madness, with players locating a puck and guiding it through twelve levels. The key word is ‘playerS’ – this is a competitive head-to-head game, with the two players starting from different points and thus competing to ‘tackle’ each other for the puck.
We know that a C64 version was at least planned – http://hol.abime.net/1979 mentions that loading instructions are included in the manual. Philippe Banwarth was behind the Amiga version, and Laurent Genelot and Jean-Paul Mari were involved with several of the company’s few C64 games, so they are also potential leads.