Thank you so much for the wonderful review. It was a really nice thing to wake up to today, especially considering how sick I've been.
Good news is, your suggestion for improvement has already been taken care of. I've been working really hard on the game ever since the contest ended. Lots of bug fixes, control improvements, level design tweaks and tuning. There's also more tutorial levels now that will come before the level you mentioned. I'm hoping this will help players feel more comfortable with the controls before I start challenging them a little.
As soon as the contest results are in, I will be uploading all of these changes in a 20 level demo.
I'm really glad you felt this game felt very retro, and fit the theme. I'm very fascinated with the ZX81, and I've been wanting to design a game in its style for a long time.
I'm also very happy you thought the graphics looked great. That was the hardest part. I was only allowed to make the graphics using characters from the ZX81's 128 character set. Each character is 8x8 pixels, and cannot be rotated, flipped, scaled up or down, or be manipulated graphically in any way. What I had was what I got. I also had to follow a "no transparent pixels" rule. So, it was quite the challenge, but I weirdly find those kinds of challenges fun.
Anyway, in closing, I just want to say thank you again, and I'm glad you liked Super Block World. Hopefully it was able to engage you enough to want to try it again once I'm allowed to get the updated demo up. :)