Reached for: Table-Tennis

Rivalry runs at full strength inside a very small permitted area, executed with precision and never once named as rivalry. The narrowing was learned in a family where competition was fierce, envious and entirely underground, so ambition had to be expressed in miniature and by symbol. What it asks for is one contest entered openly at full size.

I keep it inside the lines. That's where I win.

Arachne at the loom, whose flawless work was a challenge she would not speak aloud, and who was answered anyway. The form implies a task of naming the challenge before the weaving does it.