There are quite a few really useful keyboard shortcuts available on lesson pages, and some of them are not even completely explained under the "?" symbol in the bottom right corner, so I thought it would be useful to post a little reference guide here:

Navigation:

Left and Right arrow keys – move to the previous/next highlighted word

Shift+Left and Shift+Right – go to the previous/next page

b – jump to the next blue word

+ (plus) and - (minus) – increase or decrease font size

Space – stop/play audio

On any word (blue or yellow), you can do the following:

k – mark the word as known

x – "ignore"

f – open the preferred dictionary

s – play the automatically generated text-to-speech audio

On a blue word:

Up and Down arrow keys – move up or down in the list of hints and dictionaries

Enter – create a lingq with the selected hint or open the selected dictionary

e – like enter, but additionally opens a popup with the preferred dictionary

h – creates a new (empty) lingq and focuses the "hint" text field

(Shift+f – flags selected hint as wrong)

On a yellow word (lingq):

1, 2, 3, 4 – change the status of the word

h – focus the text field with the hint

t – add a tag

Hope this helps :).