I felt like it was a little too easy, but I'm a digital artist and I was using a tablet.
Some of the lines were inconsistent. There were really small curves that would give you a ton of points for just hovering your mouse over them (sheep), and then there were long lines that would force you to whip the mouse back and forth (fir tree). It would've been more consistent if you had players trace over straight lines instead of having the line automatically draw upon connecting two distant points.
The graphics were cool. Some of the bonus notifications were obtrusive, they should have been moved or made transparent. I think you should have gone a little further with the "comic book artist" theme and stylized the menu options in comic type.
The gameplay got boring after a while. Continuing with the comic artist idea, it would've been an interesting flow-breaker if there was a stage where you draw a whole comic page, but that's just my personal opinion.
The reticle should have been changed to something like Photoshop's precision drawing reticle. The default mouse cursor isn't really a problem, but using a drawing reticle would have added to the mood.
The time system was a little strange. I never really felt any danger of running out of time, but I'm watching the solution video and it looks like the time bonus drops down to 0.05 seconds per point. How about allowing players to adjust the difficulty, which would change the amount of time rewarded for each point? I want to try harder levels, but as it is, I don't see any way to get there other than by grinding through all the previous levels, which would be time-consuming and boring.
I thought the funnest moments were when I recognized what I was drawing. The letter hints at the top were a nice addition.
In conclusion, the core idea is original and cool, but there are a lot of tweaks that can be made to improve the gameplay experience.