because there is always more than the surface

Here’s a game I played recently by correspondence:

As you can see, I managed a corner invasion in the top-left quite early. Both players left it alone, black assuming it could be killed easily, white assuming the unusual distance to the principal wall below meant it would live easily. In the end, it was a knife-fight for seki, which I lost due to the aji of the black triangle at the bottom centre.