Basic Is Basic, that's for sure. Even the flaws are basic.

The square you control is not particularly fun to control, this is due to Basic's Basic nature. This does not justify the somewhat janky movement speed as the character snaps along large units of distance. (changing this would require reworking all the levels though so maybe not this time)

Next on the menu is something you can fix with relative ease: SCROLLING

The way the screen scrolls is worse than the original sonic games (they kept sonic dead center on the screen) basic has the screen scrolling BEHIND the player character, this results in reduced visibility. (NOT GOOD FOR PLAYER RETENTION)maybe have the screen scroll after a duration as opposed to when you go a certain distance to either side,this would allow you to make the screen scroll ahead of the blue square

finally the levels seem barren at times with huge empty spaces and a repeating background, maybe add more obstacles to them where necessary to keep the action going