Does that ever happen to you?  That an idea detonates over your head, shooting up like a colossal cartoon exclamation mark?  A vivid and unusual way to convey moments of piercing breakthrough.

‘But it was in the transept of the cathedral that the notion suddenly took shape, detonating over my head and shooting up to triforium-level like a giant exclamation mark in a strip cartoon.’

Source: Patrick Leigh Fermor, A Time of Gifts: On foot to Constantinople: from the Hook of Holland to the Middle Danube (London: Penguin Books, 1977), p. 101