Spreadsheets support gradual enrichment by allowing you to quickly put text and numbers in arbitrary boxes as if using a pen and graph paper, do basic math as if using a calculator, move things into neat rows and columns when you find yourself making comparisons, and add more formula-driven cells and labels if/when necessary as your model evolves—incrementally building dynamic complexity over time. On one hand, interesting dynamic behaviors require that the computer have some understanding of the intent of marks, and recognition of inked marks feels like a natural way to interact with a programmed system.