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Imagine that Sally has just opened up the PennyPincher website... 
FIGURE 1
Figure 1 displays the home screen of the application for Sally Smith. In this screen, she can see a list of all of the people she has a PennyPincher connection with. Each row itself is a link to a screen displaying all debts for that particular person (Figure 2). On each row, three main user interface devices are shown. On the very left, there is a checkbox used for selecting the user when Sally wants to delete a connection with that particular user. To the right, there is, on some rows, a button with a label representing the number of disputes that particular user has with Sally. Next to the disputes button, there is a convenient "add" button that will bring Sally to the pop-up add screen (Figure 3). On the very right, there is a value of how much money that Sally owes or is owed by that particular person. (Negative sign (-) means Sally owes the person, and positive sign (+) means that the person owes Sally).
Imagine that Sally has pressed the row with "Roommate #1" 
FIGURE 2
Figure 2 displays a screen displaying all of the debts between Sally and Roommate #1. The layout of Figure 2 is consistent with Figure 1, with the difference being listing debts instead of people. Just like before, checkboxes are on the very left of each row to perform row selection for the "delete", "nudge", and "dispute" functions located at the bottom of the screen. On the right side of some debts, there is a dispute flag, indicating a dispute on the debt. On the right side, the amount of debt is once again shown, using the same (+/-) system to indicate the direction of the debt.
Imagine that Sally presses the Add button on the bottom left of Figure 2. 
FIGURE 3
Figure 3 displays the add debt pop-up screen. The idea behind that idea of an add "pop-up" is that users can add a transaction from home page (Figure 1) as well as a user's page (Figure 2). This duplication may seem ineffective, but since "add" is such a commonly used function, users would appreciate not having to go back to a certain screen to "add." The add pop-up itself is pretty simple, with three main fields: name, date, and amount. The user can simply click on the field to bring up a suitable keyboard (on touchscreen phones) or simply click the field to gain focus to type. At the bottom, there is a simple add button to submit the debt. After this is done, the pop-up simply disappears.
Imagine that Sally is on Figure 2 (the page displaying all of Roommate 1's mutual debts), selects two items (checkboxes on the left are checked), and presses the dispute button on the bottom right corner. This would send a dispute in the system to Roommate 1. 
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FIGURE 4
FIGURE 5
FIGURE 6
So now, imagine that you are Roommate 1 and you are looking at the Penny Pincher application. On your home screen (Figure 4), you see that Sally Smith has disputed 2 items based on the red button next to her name. You can simply tap that button which will bring you to Figure 5. On this page, you see the items that Sally has disputed. Here, you have the option of settling the dispute (button at the bottom). This will lead to Figure 6.
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Figure 6 shows the "settle dispute" pop-up menu. In this pop-up menu, there is a "new amount" field that is defaulted to $0.00. This default has been chosen to make it easy for users to accept disputes (clearing the debt). This type of menu also makes it easy for the two users to agree on a new amount of the debt if they choose so. if the new amount is set to $0.00, the debt will be automatically deleted on both of the user's accounts. if the new amount is set to $0.00, the debt will be automatically deleted on both of the user's accounts.
Learnability:
- Pros
- Simple, table style interface.
- No “settings” menu to complicate things
- Large, easy to hit buttons (on touch screen phones)
- Consistent, clean layout
- Cons
- Multiple row selection can be confusing
- (+/-) labeling for types of debt can be very jarring at first.
- Labels and Buttons are on the same row (“Disputed” label vs “2 disputes” button which can lead to some confusion
Efficiency
- Pros
- Add function is very efficient (you don’t have to click on a person’s name and go to their screen to add a debt – you can do it from the home page.
- Clean layout lends to easy, efficient navigation.
- Multiple row selection is VERY efficient for mass deletion, “nudging”, or “disputing.” (I personally incorporated this because I hate how the iPhone lacks this feature in many places).
- Cons
- Adding an actual debt may be slow, since there are three fields to manually fill out
- No aggregate view of all transactions over some past period of time (for those who like to analyze their past lending/borrowing behavior).
- Adding multiple people quickly will take the user some time since the “add user” button only allows the user to add one person at a time.
- Users cannot add debts for multiple people at once.
- Ex: The user pays for 3 other people at dinner and wants to put down a debt of #bill/4 for each of the three other people at once.
Safety
- Pros
- Most execution functions are located at the bottom screen, decreasing chances that the user will hit one by accident when trying to hit a particular row.
- Deletion of something a user added is possible, thus making faulty added debts easy to remove and fix.
- Cons
- Deletion and Dispute functions execute immediately, with no easy way to undo the action
- Deletion action is available for debts, so technically, someone could just delete all debts even though he/she has not repaid the lender
- “Disputes” button is on each person’s row in the main screen. This can be accidentally hit when a user tries to just click on a person’s row to see all of their mutual debts.
Design #2 Storyboard
Upon logging in, the user will be greeted by the Home Page. At the top, there is a bar with the PennyPincher logo and three menu buttons to be displayed on all pages. A the home page specifically (which can be accessed by clicking on the PennyPincher logo at the top), the user will see a quick overview of the current “what is owed” status from the most recent closed transaction period. Reds (as taken from the term ‘in the red’) shows what the user owes other people, whereas Greens (for ‘in the money’ where green symbolizes as such) shows what other people owe the user. The Reds and Greens can be expanded and contracted as needed and will show the transactions under each with additional granularity.
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Complex transactions: Consider the case where at a dinner, a group of 4 decide to evenly split a $100 dinner bill. However, some people are short on cash while others have extra on hand. So one person pays $50, another $40, and two of them $5 each. If in the end this should be equaled out such that all pay only $25 for the dinner, how would that happen? The solution to this is currently unknown.
Design #3 Storyboard
From the home screen, the Sally can click a button to add new transactions. This will take her to the “Add a Transaction” page. On this page, she can select a user from a dropdown list of know users or search for a new user by clicking on the “New User” button. A text box allows her to enter the amount of money the selected user owes. Clicking the “Submit” button records the transaction for Sally and the selected user, and brings Sally back to the home page. Clicking the “Cancel” button brings Sally back to the home page. The home page will also have a “Pending Transactions” button with a number displayed next to it. Clicking this button leads Sally to a page that shows any new transactions where other users claimed that she owes them some sum of money. Sally can dispute claims on this page by clicking any of the dispute buttons next to the individual claims. Clicking the “Done” button brings her back to the home page. 
From the home page, Sally can view all current transactions she has with other users. If Sally wants to view all transactions, including past transactions, she can click on the “View All” button. Clicking this button leads her to the “All Transactions” page. This page shows two lists. The list closer to the top of the page shows current transactions she has with other users. The list below the current transactions list shows past transactions she’s had with users. The past transactions list does not include the amount of money because these transactions should have all totaled out to $0.00 since these are closed and settled transactions. In both lists of transactions, you can click the button corresponding to each user to view all transaction history with that particular user. This leads you to a different page, which displays a list of dates and money amounts for every past transaction Sally has had with that user. 
Suppose Sally wants to dispute a transaction with Bob, she can do so by viewing the details of her transaction with him. This will lead to a page that shows the total that she owes Bob, or however much Bob owes her. This also shows a list of dates and money amounts for every past transaction she has had with Bob. Next to each transaction where Bob claimed that Sally owes him money, Sally can click the “Dispute” button if she disagrees with that transaction. The “Done” button brings the user back to the home page.
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