Casual Chess is a clean browser chess game with three computer difficulty levels and a choice of board themes. All the standard rules are implemented — castling, en passant, promotion, stalemate — so it's a real game rather than a simplified one.
The easy setting is genuinely beatable by a beginner, which matters: an opponent that only ever crushes you teaches nothing.
On easy, yes — comfortably, for a beginner. Moderate punishes loose play and hard requires real attention.
Yes, including castling, en passant capture, pawn promotion and stalemate as a draw.
Yes — tap a piece then its square. Nothing to install.