Python has two types of statements; "simple" statement and "compound" statements. Compound statements are those, like the if- and while-statements, which require multiple lines.
Only simple statements may be separated by a ';', not compound statements.
This is a bit different than what you wrote. For example, "x=4" is a statement, and not an expression, but "x=4;y=5;z=6" is a valid Python line because assignment is a simple statement, and multiple simple statements may be separated by a ';'.
While it was far better (and thanks for the pointer to Cathode!), I figured out what the problems are. First (and probably most important), the lines being output don't touch each other, so there are horizontal gaps across the entire screen. Second, the glyphs are much thinner, reducing the feeling of "wall".