Nice submission! I enjoyed the tutorial and got to about 3000 in the endless mode. Cool idea that the colours would change with an increased high score! Aside from it being highly polished, I do have a few critiques to mention:
- The "big block appears right under a little block" does create a weird object that acts like a destructible block, but you can also pass through it? It may be a part of the "blocks spawning under tanks" you mentioned earlier, so it may just resolve itself in the end. ^^;
- The higher speed you attain, the harder it is to move your tank into 1x1 spaces. I'm not sure if that's intentional or not, but that's up to your design.
- I noticed the view's resolution is interpolating, although the view area conforms to the 64x64 requirement. I believe while installing the game mentioned that it was made in GM:S2. Is there a similar work-around akin to "surface_resize(application_surface, 64, 64);" from GM:S1, or does your game use more complex surfaces than a simple line of code could fix?
Other than those random opinions of mine, great job!