When building on a budget you regularly cannot design a model and then build it without purchasing new pieces. I learned this lesson the hard way. Instead of designing first and then building your model I found that putting pieces that seem like they have a lot of potential together, you can create a model that looks like you designed it. Another method of building with a limited supply of bricks is having a vague idea of what you want to build and then try to build that idea as best you can. For the model shown below I used the first method described above.
No, this MOC was not inspired by the turrets in portal at all. It was only after completing the model that I saw the resemblance.