OK, let's start off with some context first. Legend of Zelda was created for Nintendo's home video game console "Famicom", or the "Nintendo Entertainment System" (often abbreviated NES today) in America. This console uses a MOS 6502 based CPU containing about 3500 transistors running at just below 2 MHz. To compare, a modern current year smart phone might have a CPU with a million times more transistors and be running at a thousand times the clock speed, with performance easily tens or hundreds of millions of times greater. The NES and other gaming consoles of its generation had very limited capabilities. The vast majority of early video games in the 1980s were pretty simple with small codebases.

Low resolution, simple graphics, simple sound design (very "beepy"), simple and typically repetitive game mechanics, etc. Classic examples being Pac-Man, Asteroids, Frogger, and Pitfall! The core of game play would typically center around a single screen with a few low resolution sprites moving around it and some fixed background graphics (Pac-Man being a perfect example of this). For many games a single screen was a whole "level", and when you beat the level within some time constraint you could move on to the next level, another screen with a different layout and similar but slightly different mechanics and graphics. Some early games, like Pitfall!, were a little innovative in that they connected different individual screens together to make them feel like part of one bigger level, when you got to the right of a given screen you'd load into the next one as a continuation and be reset to the left of the screen. However, many of the individual screens were very similar.

This era of games, even in home consoles, was dominated by arcade fare. Fast paced games with time limits that required quick hand-eye coordination and usually reset back to the beginning after some number of "losses" (losing lives, etc.), often married with blaring and simplistic sound tracks and sound effects. Precisely the sorts of things that eat quarters, attract attention, raise tension, and trigger a feeling of accomplishment (or loss) in an arcade setting. Many of these games were very simple, being created by small teams of a handful of people (or in some cases even individuals) over a few weeks of work in some cases. This made them intensely profitable, both for game makers or distributors, arcade operators, and console makers, which was why they were insanely plentiful through the mid-1980s. So much so that it actually crashed the entire video game market in the US in the early '80s.

This is the backdrop into which the games Super Mario Bros. (1985) and Legend of Zelda (1986) were released (both for the Famicom/NES), both of which pushed the boundaries of what a video game could be, how it looked, how it sounded, and how it played. In Super Mario Bros. (SMB) each level is many screens wide, but they are not fixed screens in the sense of Pitfall! or many other games, the character stays roughly in the same part of the video screen the whole time, but the view smoothly scrolls from left to right as the player progresses through the level. SMB wasn't the first game to introduce this kind of gameplay but it pulled it off incredibly well. SMB also introduced a variety of other innovations, a control system that was smooth and responsive compared to the more chunky systems of other games. It also used higher resolution sprites that were very cleverly made to make the most use of the limited memory available, making the characters in the game (including the player character) look more like recognizable cartoons than blocky blobs. It also leveraged the limited sound capabilities of the console to produce an enticing and fun (and now iconic) music soundtrack which changed in different levels, adding a bit of atmosphere to the game from sound design alone. On top of that the game used subtle tricks and techniques to make each level feel more interesting and more "real". Levels often had alternate routes either above or below the main path, there were sometimes secrets (hidden coins or blocks or power ups) to encourage exploration. For example, there are "underground" levels which are very similar to the above ground levels except with a different color palette, different graphics, different music, and the player "falling" into the beginning of the level instead of just starting on the ground. These simple tricks made it possible to take the core gameplay and level design systems and tweak them just slightly (which was hugely efficient in terms of memory requirements) to make them feel very different, and in total the result is to make the whole "world" of the game feel much more expansive and full of diverse and unique individual areas than the game would otherwise. The overall result was a game that felt like it had a stronger "character" and aesthetic than many others, and felt like a much bigger and more interesting game because of those aesthetic game play touches. However, SMB still retains a bit of arcade heritage by having a series of specific levels to complete within time limits and a fixed number of lives in order to do it in (as well as a score).

The Legend of Zelda game builds on a lot of these aspects in its game, but makes a lot of dramatic diversions as well. Much like SMB, Zelda heavily leverages a compelling soundtrack and clever artistic/color palette choices to make the game feel like it has a huge number of different and diverse environments, not just one. Zelda uses a top-down view instead of a side-on view (like SMB), and focuses much more heavily on the exploration and adventure aspect than twitchy, high-skill gameplay (although that's still somewhat part of the game). Zelda uses a system of single screens tied together through their edges to give the illusion of a larger world / level in a similar way to many other games (even going back to 1980's Adventure for the Atari 2600) but it links things together much more smoothly and seamlessly than the typical game of the time. Zelda also does something very clever in layering or connecting different sub-worlds together to make the entire game feel like it's one huge adventure. There is the "overworld" of the game which is a fairly large rectangular grid of many individual "screens" or areas, all aesthetically decked out to give the appearance of being different parts of a large landscape, with some areas filled with mountains, others filled with forest, others with lakes or oceans bordering them, etc. Within this overworld there are places where you can "enter" other areas, if you take your character through the entrance on the screen the game loads another screen, and there's a whole different environment there. These can be simple such as little caves that are shops or that have clues or story elements in them or they can be entire multi-screen "dungeons" that are like like sub-games all their own. This is one of the genius things about Legend of Zelda in that it ends up being not just one simple game the way many earlier arcade style games were but a whole series of slightly different games all packaged together and meshed with each other that makes it feel like a single expansive world with exciting and diverse parts within it. There is a bit of cognitive trickery here in that the "overlay" of the dungeon levels and the overworld is more representational than it is literal, the dungeons together take up the same expanse of space (screen by screen) as the entire overworld, but it feels like the dungeons are smaller than the overworld, a bit of narrative trickery that players just accept intuitively and don't think about much, but which aids gameplay in making exploration of the overworld feel more expansive as traversing a few screens in the overworld has the "feel" of moving across a continent, not just walking a city block or two. Again, all aided by the music, graphics, and gameplay which support these feelings.

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