Hi Gigi! I downloaded Block 64! and gave it a whirl.
What Works
First things first: thank you for paying attention to your app manifest and not spamming me with a bunch of permission requirements no game should actually need. That’s one of the first things I look at in an Android app, that people keep getting wrong. It’s a technical detail, but it’s worth mentioning. It shows you paid attention when building the game.
The game is mechanically simple in a good Tetris-way. It (mostly) makes immediate sense. Your tutorial is simple, but helpful, and doesn’t last too long - it helps me figure out how you’ve intended me to interact with the game.
As @GarBenjamin said, no ads. This “bug” you’ve noted is actually much appreciated, but I think that the ad would be OK on the final score page.
What Doesn’t Work
Your presentation is overly simple. I feel there’s a lot of room for visual polish, given the simplicity of the game. Specifically, creating a bitmap font that suits the feel of your game that is stylized to the aesthetic of your vision for Block 64! would beat the holy heck out of that awful Comic Sans font. The individual blocks and the background could work really well with some subtle details. Your first screen has a good aesthetic that with some slight, subtle detail, makes an excellent model for the rest of your game. You’ve got a strong mechanical base and a strong first screen, so go ahead and put a little time into ornamentation on the whole project!
Speaking of the mechanics there were some unexpected row-clears I got. I’m not entirely sure if it was a row that I finished without realizing it along an axis I wasn’t paying attention to, or if the colors on the blocks actually mean something. This is one thing your tutorial doesn’t help with, because the tutorial blocks are all the same color; if colors matter, that’s a detail you’ll want to build into your tutorial. If colors don’t, you should also build that into your tutorial!
The background soundtrack is OK; it seems almost like clip music (e.g. not a great thing.) Some way to control the music and sound settings would be very welcome, because different players have very different aural tastes, but if possible try to add more variation to your game’s soundtrack. The music is very a cosmetic option, so a little more choice wouldn’t hurt - other players will certainly appreciate it!
The TL;DR
You’ve got a really strong base game. A little bit more polish will help raise this simple, fun time-waster to the next level. Great work, Gigi!