(;
AB[ca][cb][bb][bc][cd][ce][cf][bd]
AW[cc][db][dc][da][de][dd][df][eg][cg][bg][bf]TR[bd]
C[White pushed into black's group, and black defended with the marked stone.
He's still not safe though... show me why not (without a ko).]
PL[W]
(;W[ad];B[ac](;W[aa]C[];B[be];W[ae];B[af];W[ae]C[RIGHT])(;W[ae];B[aa]C[Black is alive])(;W[be];B[aa]C[Black is alive.]))(;W[be];B[ad](;W[ab];B[aa]C[Ko.])(;W[aa];B[ab]C[Black is alive.]))(;W[ae];B[ad](;W[ab];B[aa]C[ko.])(;W[aa];B[ab]C[Black is alive.]))(;W[ac];B[ad](;W[ab];B[aa]C[Black is alive.])(;W[aa];B[ab]C[Black is alive.]))(;W[af];B[ad](;W[aa];B[ab]C[Black is alive.])(;W[ab];B[aa]C[Looks like a ko, but will it work?];W[ba];B[ac]C[No, this is not even a ko, because of the damezumari (shortage of liberties).]))(;W[ab];B[aa](;W[ba];B[ac]C[Because of this damezumari, shortage of liberties, black is alive])(;W[ac];B[ad]C[Black is alive.])(;W[ad];B[ac]C[Black is alive.]))(;W[aa];B[be](;W[ab];B[ae];W[ac]C[Bent four in the corner. RIGHT])(;W[ae];B[ad];W[ab]C[RIGHT])(;W[ac];B[ab]C[Black is alive.])(;W[ad];B[ae]C[Black is alive.])))