Hiya, had 4 to 5 goes at it, i really like this change but lol:
1. Because of the increased fire rate I can literally stay on one side and stop 90% of the sharks coming up so I think the speed of the sharks need increasing by about 20% at level 12 then staying at that speed.
2. I've really noticed the speed increase of the sharks coming at the player and I feel the speed they come up at level 11 is perfect, anything past that and even I can't react in time lol
3. The font on the original game with the number 7's they are like hooked over the top (See image) Also the score usually starts with one "0" and yours starts at "00"
Conclusion, what I think may be best
Levels 1 > 7 are fine the way they are. From 8 > 11 the sharks swimming towards the diver is increased upto level 11 as this is plenty fast enough. At level 12 the sharks at the bottom speed up by 20% ish but stay at that speed throughout if this can be done :)
Cheers
7 font in the original game