Update: This issue has been patched (yay!) however there is still discussion regarding drawing efficiency. I used this project to determine the exact conditions that cause Scratch to fail to draw a dot upon pen down. It appears that drawing a dot fails if and only if: ( 0.125 < ( x mod 0.25 ) < 0.175 or ( x mod 0.5 ) > 0.25 and 0.125 ≤ ( x mod 0.25 ) ≤ 0.175 ) and ( 0.125 < ( y mod 0.25 ) < 0.175 or ( y mod 0.5 ) > 0.25 and 0.125 ≤ ( y mod 0.25 ) ≤ 0.175 ) Hence, a possible workaround for this issue would be to transform the sprite's position to [ round( x * 16 ) / 16 – 0.0001, round( y * 16 ) / 16 – 0.0001 ], which produces less significant rounding artefacts than simply rounding the coordinates, but requires more computation. However it may be more appropriate to use the 'move 0.5 steps' workaround, which draws a 0.5 pixel long line segment, only very slightly elongating the dot. (See @jgordon510, http://scratch.mit.edu/projects/36235410/) This issue in the bug tracker: https://github.com/LLK/scratch-flash/issues/482 /// Using the program (for the sake of completeness) /// The square of dots represents one pixel. Press space to run a scan in the upper left corner pixel, plotting purple dots at the corresponding points within the square when drawing succeeds. This does not work properly in turbo mode. Press R to change the scan resolution. Once a scan is complete, press B, then click and drag across a single boundary FROM purple TO white, and the program will search for the point (as an offset from the lower left corner of the pixel) where the drawn line intersects the success-failure boundary. After clicking again, B can be pressed again. Press C to test a particular pair of offset coordinates. Press K to test all of the four edges of all 16 square failure regions.
