Klondike
Klondike is the solitaire — the one that shipped with every office computer and quietly consumed a decade of global productivity — in a stylish HTML5 deal: seven columns, four foundations, red on black, aces up.
Clean animations, generous undo, and the exact 3-minute round length that made it immortal.
Tip: empty a column early even at the cost of "wasted" moves — an open column is the engine every winnable deal runs on. More patience (all kinds) at solitaire games.