This is a fairly difficult review to write, because talking about this short, free, browser-based game pretty much undermines the main pleasure of it, which is understanding it. Simply put, But That Was Yesterday is a metaphorical/symbolic walk through dealing with stress and lingering emotional issues, with platform jumping. Yeah, I know how that sounds. Really, it has to be played.
There are no real instructions or guides, and only 3 controls: left arrow, right arrow, and up arrow, and you're pretty much told which you can press at any given point. Mostly, you are trying to unlock and resolve a story, and you do this by playing through some fairly simple stages.
Your character is a nameless man, and the other characters--another man, a dog, a woman, some others--are equally nameless, though they are referred to by color or role--the golden dog, the green friend, etc. You travel through a series of abstract landscapes, fields, and city roof tops. It isn't possible to lose But That Was Yesterday, though there are multiple endings. Figuring out how to get to them is part of the fun, so it will not be revealed here--and the author states there is no "right" or "wrong" ending, just different ones. (A small hint: The usual methods of finding alternate paths or Easter eggs probably won't work; the key is fairly unusual, though I'm hesitant to use as broad a word as 'unique' given how many thousands of games are out there.)
The look of the game is intriguing, a flat and slightly caricatured style that focuses on reducing things to their most essential shapes, while never leaving you confused as to what something is supposed to be. It's reminiscent of author OneMrBean's unrelated [Together], an award-winner in Casual Game Design Competition #8: Sandbox. But That Was Yesterday's soundtrack is wonderful and neatly complements and enhances the sense of mood upon which But That Was Yesterday focuses. It's so popular, in fact, that the author plans to release it (for free) in the near future.
Playing the entire story (regardless of ending) from beginning to end takes only a few minutes, and you'll probably know in a minute or so if you want to finish it or not. It's certainly not for everyone--it's abstract, symbolic, emotional, and more about evoking mood and understanding than it is about killing things, solving puzzles, or unlocking achievements. But That Was Yesterday qualifies as a "game" only by a fairly loose definition; it's more like a short story in which you need to solve a puzzle to see the next page. If you like it, it will be several minutes well spent; if you don't like it, you will lose only a minute finding this out. Worth exploring.
Note: To play this game, you must follow the link and open it in a Flash-enabled browser. After two brief ad videos, you can play the game online. This game won first place in the Casual Gameplay Design Competition #9: Friends.