Weight

In icn you can set the pen width of the subsequent rendering using the w command

w 10

Setting the size to 10 makes the line thick!

w 10
line -10 -10 10 10

w 2

We can use a smaller line weight by simply using a smaller number

w 2
line -10 -10 10 10

As you can see, the line weight affects the width of the line, allowing you to make more intricate icons using different levels of weight.