The most famous videogame character of all time is (with apologies to Pac-Man) Mario. I would therefore be amiss not to feature one of Mario's earliest adventures. Of course, I've already missed the 30th anniversary of the very first Mario game, Donkey Kong, which premiered in 1981. However, when that game first came out, the protagonist did not yet have the name "Mario" (he is referred to as "Jumpman" on the cabinet). The first video game in which Mario is referred to by name is our subject for this month: Donkey Kong, Jr.
The context in which Mario's name first appears also sets the stage for the game. Mario (two of him, oddly enough) is seen raising a caged Donkey Kong to the top of the board, and then moving the cage over to the side. The player is then given instructions to "save your papa!", and the game is on! Notably, Donkey Kong, Jr. is the only time Mario is ever the antagonist, rather than a heroic figure, in a video game (and that's saying something, given that Wikipedia places Mario in over 200 games over his 30+ year history!).
Like its predecessor, Donkey Kong Jr. is a platform game where you try to move your character from the bottom of the board to the top while avoiding various obstacles along the way. The main difference derives from the basic role reversal, whereby you're now controlling the ape rather than the human. Thus, although there is some amount of walking and jumping along platforms (as in Donkey Kong), the bulk of the time is spent climbing and swinging along various vines and chains. On most levels, the idea is to get to an area near the cage, where a single key awaits. Once you get too close to the key, Mario pushes the cage away, and you have to follow him to the next board, eventually reaching the board seen here (the last of any given level), where Junior must push each of the keys to the top of the board from underneath, thereby unlocking a portion of the cage imprisoning Donkey Kong. Once you accomplish this feat, father and son are reunited, and although Mario chases after them in a futile attempt to recapture them, Donkey Kong sends Mario flying across the screen with a well-placed kick. Of course, as with most video games of this era, such victories are fleeting, and you start off with the first stage again, only with greater difficulty (Mario must have recaptured the big ape off-screen, but don't ask me how).
It's already no simple matter just to get Junior across each board safely, but if you really want the big points, you have to take advantage of the fruit that hangs on various portions of each board. As Junior passes over a piece of fruit, it falls down the screen, knocking out any enemies unfortunate enough to be in the way. If you're able to catch multiple enemies with a single piece of fruit, you can get geometrically higher points for each additional enemy caught. Wikipedia cites the current record score at 1,307,500. Wanna try to beat it? Good luck!