Computers have gotten smarter over time, a lot smarter. You've probably heard of Moore's law. It's hard to appreciate the vast amount of RAM our modern laptops and phones have in comparison to earlier computer.
The original Apollo guidance computer had 2048 words of RAM. Each word is 16 bits, bringing the total RAM to 4kb.
It was used in the Apollo program to plan the route of the Command & Service module and Lunar Module (citation) and was an amazing piece of kit at the time (1966 - 1975).
These days, few popular web pages can fit in 4kb. I don't think that's a bad thing, though it gives us some room for improvement. It's just a part of the cost of all the improvements that we have made.
It turns out that there's still a lot that can be done in just a few kilobytes and there are a bunch of competitions that are centered around this. The most famous of which (that I know of) being the js1k competition.
The aim is simple:
Make a game in JavaScript that fits in 1 kilobyte!
You can minify, compress, use terse style, anything, as long as it fits in 1kilobyte.
The js1k competitors are pretty amazing, I recommend playing a few of their games (they download really quickly too).
1kb is pretty restrictive, and I was (and am) pretty new to code golfing, so I have yet to try the 1kb variety. However, a friend of mine is a pretty awesome web developer and invited me to compete with him in the js13k competition. It's basically the same as the js1k games... but as you can probably guess, you get 13kb.
So, with 13kb to play with we could implement almost anything we liked, and definitely more things that we had time for writing from scratch.
Here's our entry on js13kgames.com
And here's Sam's site.