Click the green arrow to start the game. Audio on! First, it will play the tonic (Do, in solfege -- major only for this project). Then, it'll play another note. It's your job to use the left and right arrow keys to move the pink dot to the correct solfege for that second note, relative to the tonic provided!
I was very much a choir kid in high school, and one of the side effects of that is that now I hear solfege in almost any song you play for me! (Seriously, play music for me, and I'll sing along in solfege, not lyrics. It annoys my friends, and is less impressive at parties than one would expect.) That took a lot of practice, and this mini-game is a microcosm of what that kind of practice sometimes looks like. If curious, solfege are the notes you see on this screen -- Do, Re, etc. -- that represent relative pitches in a given key. So no matter the key, the relationship between Do and La, for example, is the same. This game tests out your relative pitch in three different keys: C, F, and G. With more time, new keys could be added -- and, crucially, more sounds (Scratch doesn't have any accidentals built in, so something like Db major is kind of out of the question right now). With gratitude to my middle and high school choir directors, Ms. Abrams and Mr. Cushing, respectively, for making me a nerd for solfege. :)