Strengthening - tells me that I have practised something when I haven't...
Sorry to have to use a discussion to report an oddity, but there seems to be no other way in this case.
Having got to the end of the course by using a mixture of testing out and going through some of the lessons, I have just done a short session of 'strengthening' by using the button on the right-hand side of the screen. What came up was mainly the 'rhaid i...' patterns. When I finished it told me that I had just strengthened the imperfect, but I do not recall any imperfect tense items coming up at all.
Similarly, I was told 'places' when I had mainly done colours.
Even the skills that introduce grammar points usually also introduce new vocabulary; if you had sentences that included that vocabulary, then by strengthening those words you also strengthen the sentence that those words "belong to".