I have seen this before and I just realized that there is a lightning bolt made with negative space between the "l" and the "t". It is very basic but I gives off a feeling of electricity, even if you do not see the hidden lightning bolt.
Don't text and drive: you either see the letter or the danger. This is a fantastic example of how clever use of space can make a big impact. An innovative idea that really drives home the dangers of while driving. by Leo Burnett for FIAT