Up and Down and Up and Down

[firebreed]

Hi. I have an idea for an art i'm working on but kinda 'stuck' trying to figure out the following.

 

It's like lines (with different thickness) going up and down when it intersects (i wonder if thats the correct word..my English kinda 'Booleanic'..haha).

 

Check out the screen. If just using Loft and one circle/square then it would be a snap of the finger, right? But then i want it with different thickness (artistic flow). BTW, the lines should be solid.

 

Ideas on how to accomplish this is much much appreciated.