Mahjong Solitaire Online

You clear a layered stack by matching identical tiles, but only tiles with a free edge can be taken. That restriction is the game - the tiles you can see are not always the ones you should remove.

Usually because of an earlier choice. Taking an easy pair can bury the tiles underneath, so when several pairs are available it is worth taking the one that frees the most rather than the one you spotted first.

Mahjong Classic. It uses the standard layout with no extra systems, which makes it the cleanest way to learn how to read a board before trying the variations.

It changes the matching rule from pairs to threes, which sounds minor and completely alters the planning. Every match commits three tiles instead of two, so the board empties differently.

No. The four-player game is a completely different rummy-style game played with the same tiles. Mahjong solitaire is single-player tile matching, and it's the version almost everyone means online.