Spirit Billing invoicing software

As a final project for INST631 (Fundamentals of Human-Computer Interaction) at the University of Maryland, I designed a new technology to be used by the Ghostbusters.

I created a product called Spirit Billing. Spirit Billing is a piece of client invoicing software that can be integrated directly with the Ghostbusters’ existing ghost trap technology. Spirit Billing can be used to generate an invoice and/or charge a specified client for their outstanding balance based on the contents of the ghost trap. I believe my final product could help the Ghostbusters conduct business more smoothly without modifying their existing ghost trapping protocol.


Problem to Address

After capturing their first ghost at a fancy hotel, Peter rattles off a list of various fees owed and jots them down on a paper invoice to hand off to the client. Peter has to remove his gloves to write on the pad of paper, and viewers never actually see the Ghostbusters collect payment. It would be beneficial for the Ghostbusters to have an easy way to invoice clients and accept payment onsite at the time their services are rendered, especially since their initial loan to cover their startup costs has such a high interest rate.

Design Process

Low fidelity prototype

When starting to develop my low fidelity prototype, I first identified the precise tasks I would like the user to be able to perform. My initial list of tasks was as follows:

  • Inform the system which client the trap is currently being used to trap for
  • Ghost is lured into trap and trap closes
  • Feedback provided to the user indicating that the trap currently contains a ghost
  • System confirms presence of a spirit and generates invoice for client indicated
  • Offer opportunity for client to pay immediately

I made the following assumptions:

  • The Ghostbusters want to render services first, prior to billing the client or accepting payment
  • The Ghostbusters need a way to perform the necessary tasks without using a touchscreen (in case they are on a job and still wearing their gloves)
  • The Ghostbusters charge clients fixed costs for proton charging and spirit storage
  • Only one ghost can be contained inside each ghost trap
  • Client contact and billing information is primarily entered into the system offsite, using a computer with a full keyboard

High fidelity prototype

After testing my low fidelity prototype with two people, I identified three changes to implement in my high fidelity prototype:

  1. A better way to sort through the client list, assuming that this list will eventually get quite long
  2. A way to accommodate “unknown” or “TBD” options when selecting from the client list, or perhaps a way to manually enter a new client on the fly
  3. A way to immediately accept payment from a client

I created a high fidelity prototype using InVision. I was able to have users walk through my protoype using my mobile device (a Google Pixel 2).

I used the Law of Uniform Connectedness and the Law of Common Region to develop a way to split the client list into two categories: individuals and companies. I designed the two categories to look like a set of old school file folders, and the user can use the left and right arrows to toggle between the two categories. Keeping Miller’s Law in Mind, I made sure that the client list only shows six clients at any given time (the remainder can be seen by scrolling).

I also added “cancel” and “enter new” buttons to the screens that display the client list.

At this point, I struggled with how to have the ghost trap act as a portable point of sale system. I knew I wanted customers to be able to pay on the spot, and my initial idea was to have a place on the ghost trap where you could swipe a client’s credit card. However, I decided that the ghost trap is likely too volatile to also act as a payment processor, and it would be better to just get permission to charge a client credit card that had been previously saved to the client’s file. I added a series of screens that appear after the invoice is sent asking if the user would like to charge the client’s credit card.


Usability testing

I developed a protocol for usability testing my high fidelity prototype.

© 2019 Kristen Marie Byers