Backstory: when we first set up the sandbox, we offered a handful inputs that devs could optionally use in their letters. You could click and drag directly on the letter, drag a little token on a "Kaoss Pad"-like control surface, scrub a timeline, toggle a big global mode switch, and more. Everyone used a different subset of the these inputs, based on whatever seemed like the best fit for the idea behind their letter. Some people even bypassed all that and implemented their own input handling (like Lilith did for the bullet hell game in C0). But most folks actually didn't add any interactivity at all.

When I curated the letters for our home page, I wanted to strike a balance between a few things. I wanted to encourage playfulness, for instance by having unpredictable things happen depending on what/how you interacted ("output randomness", to borrow a gamedev term). And while I did make some changes to some letters (adding some additional interactivity, simplifying some inputs), I didn't want to go too far and ruin the authorial intent behind the letters.

But, like you and the other commenter here found, there is inconsistency that errs on the side of frustrating. That's something that irked me too — I just ran out of time for polish and had to ship.

In any event, thanks for kicking the tires on it. Even if it didn't quite clear the bar for playful interaction, I hope it was fun to look at.