boop
Hee, cool stuff! I can recommend using a ruler if you want to nail perspective lines real good, given how annoyingly difficult it is to draw straight lines free-hand. Perspective really isn't as complicated as some people may claim, the tricky part is to figure out the exact size and distance of whatever you're drawing. This is probably due to the fact that our eyeballs like to use relative size to judge scale, ala EXAMPLE.
So i guess what i'm saying is that relative scale is more important than absolute scale. :vboop