my typical experience with these kinds of things: I start looking at the source code, and the code is actually simple and short, the logic is easy to follow (make a grid, allow and process formulas in cells, display the grid and some additional edit-mode display if you are editing a cell)... but then I start seeing dependencies, references to other frameworks and multiple languages, libraries... and all that looks so confusing! the dependencies require at least an order of magnitude more knowledge to be understood or used effectively than what we are being shown in the post; that's the really tricky part to me. don't mean to criticize that, those are probably very powerful tools that in most cases you want to know about and use (if you are working in that specific environment), but it's like... are those 100 lines of F# even that important? writing your own excel sounds nice, but I feel it's more "how to glue a bit of F# logic to a web-compatible UI" (well, yeah, one could argue those are really the same things).<p>> "The final spreadsheet application is quite simple"<p>Is it? I easily understand the logic of the F# code, but I couldn't make another "similar" application so easily unless I was just copying the dependencies. I wouldn't really know what I'm doing, maybe it's not so simple!<p>(this isn't meant to be a criticism to the article itself, I just wanted to share this uneasiness I get when checking some code I don't know much about that's presented as "simple"/"short"/...)