Using FlowSheet to visually explain a spreadsheet

Flowsheet helps you "see" what is happening in a spreadsheet by showing its formulas: their inputs, magnitudes, signs, units, computations, and other cells dependent on them. Below is a visual walk-through of a very simple spreadsheet, just to illustrate this new visual language.

1. Here is the original spreadsheet, charting sales of widgets. In each month, a different number of widgets is shown, costing a different amount and sold at a different price. The final profit depends on the difference between total revenue and total expense, and the average profit-per-widget is a ratio over those sums.
   
   
2. Here is what the popup FlowSheet looks like before any cell has been clicked. The cell's position (e.g. C3) is show in the cell's upper left, and its value in the lower center. If a cell is marked with "=", it contians a formula; hovering the mouse over that cell will show the formula in the control panel. More than one ">" symbol indicates the number of other cells whose formulae depend on that cell.
   
   
3. Here is the browser control panel. It lets you control which flowlines to display (inputs to formula, outputs from cells or both), and shows clear details of the formulae and FlowGraphs when the mouse is over a cell.
4. Clicking on a cell with dependent computations shows FlowLines connecting the cell to its dependents. For example, the monthly number of widgets is involved in four subsequent computations: of revenue, expense, profit, and total widgets sold.
   
   
5. Clicking on a cell with a formula (marked by "=") not only shows dependent computations as above, but also shows the formula's computation and its inputs. Here, the sum of widgets sold is composed of four separate entries from the cells above; the thicknesses of those arcs are proportional to their numeric magnitudes, and the thickness of the "output" arc is the sum of those separate widths.
   
   
6. Multiplication: The revenue calculation must multiply a cost in dollars ($1 per widget) by a number of widgets, resulting in a much larger dollar amount (the two arcs arrive at a 90-degree angle, as if multiplying to form an "area"). Both dollar amounts are in green (!), to show they have comparable units, but the $1 arc is obviously much, much narrower than the $400 arc. The output of this calculation is sent both to the total-revenue sum below, and to the montly-profit calculation at right.
   
   
7. Subtraction: The profit calculation looks like a sum, but passes onward only the difference between the widths of the input arcs, as if the two inputs "cancel out" each other leaving only a difference.
   
   
8. A profit subtraction using different numbers results in a negative output, which is shown as striped arcs.
   
   
9. A full sequence of computations--chained together--can be shown by clicking on several cells which depend on each other. This shows the progress of the computation from its most raw inputs (at left) toward the very final, processed values at right.
   
   
10. By displaying the formulae for many cells which share parallel computations (like the expense calculations for each different month), you can see the relative magnitudes of all those inputs and outputs.... among other things, this is a quick-and-dirty way of graphing the relative magnitudes of a selected subset of data. Exceptionally large values stand out, as with the third output from the bottom ($240).