Hi, thanks for playing; if the visual bug was the same as other commenters have pointed out, then I'm looking into it to prevent it from appearing in future games I make—no idea what caused it yet, though.
Thanks for the feedback on the difficult jump. In hindsight, I could have made a star system to alert the player that the number of expected points in levels 2 and 3 is 10 for one star through 25 for three stars. So instead of feeling like the difficulty is changing, it's just that the goal is changing.