l'imparfait - the imperfect in French

This is visually very effective but maybe overcomplicates the imperfect. The usual way of teaching is to base the stem on the nous form of the present tense therefore giving être as the only irregular verb. I like to give the good news that there is at least one tense with hardly any irregular parts to learn!! Thank you for a very clear introduction, particularly to the usage of the imperfect which is quite hard for students to grasp.