FreeCell is a remarkably skill-based solitaire variant invented by Paul Alfille in 1978 and popularised by Microsoft's Windows version in the 1990s. Unlike most solitaire games, almost every single deal — roughly 99.999% of them — is solvable with correct play. There are no hidden cards and no luck once the cards are dealt.
The four "free cells" in the top-left act as temporary holding spaces, and mastering when to use and when to free them is the heart of FreeCell strategy. Experienced players can solve deals in their heads before touching a card.