Fix Scroll Speed

[greggman]

Because game runs at 10fps and scroll speed is set to 10% that means for each of the 6 displayed frames of a game frame the screen scrolls at 6 different rates.

In other words, lets say the screen needs to scroll 32 pixels (one tile)

It might scroll 32 * 0.1 pixels on frame 1 or 3.2px to position 3.2
Then it would scroll 28.8 * 0.1 pixels on frame 2 to 6.08
Then it would scroll 25.92 * 0.1 pixels on frame 3 to 8.672
As you can see each frame is slower but then jumps up when the player moves further
At frame 6 a game frame ticks and now it's target is 64 pixels.

This stutter is noticeable.

A simple solution is probably just a max velocity of tilesSize / frameRate