The ships/words on screen all start with different letters. Once you type the first letter of a word, that one changes orange (and you have it finish it before your key presses will be recognized for other words).

This also applies to the single-letter bullets, unfortunately, so if you've just started typing "misappropriation" but a stray "s" is about to hit you, you're out of luck.

What got me a few times was a first-letter typo - which matched another word. Then I'd lose a few seconds just finding which word was claiming my key presses, and that'd be the end.

I didn't know Esc would work there! I'll try that next time around.