21w06a is perhaps the most revolutionary snapshot ever

Gushing

I always said that if they were to actually increase the world height in 1.17, it would change Minecraft fundamentally. I had an increase from 256 to 512 blocks in mind.

Mojang managed to blow our collective socks off with 384, and I absolutely commend the team for this incredible change.

I think back to some snapshots that were truly game-changing, such as 13w36a, the first snapshot of 1.7. Or the 1.4 snapshot that added command blocks. Or 20w06a which brought a tier better than diamond to Minecraft for the very first time in over 10 years. These were all absolute game-changers. 13w36a changed the biome system. Command blocks revolutionised maps. Netherite gave players a final late-game tier to aim towards. But this... this changes Minecraft at an even more fundamental level. This not only COMPLETELY shakes up a large area in the Minecraft world, it shakes up the core progression of the game, forever.

Minecraft as we have known and loved, has, after more than 11 years, FINALLY gotten an upgrade. For over a decade, we have come to really learn the mere 64 blocks beneath our feet like the backs of our hands. Iron and coal are at the top layers. Dig a little further down and you hit gold, which you probably bypass entirely. A few blocks further and there you have it - the best resource in the Overworld. Diamonds. The entire mining progression in just 64 vertical blocks. We have learned to basically tunnel at y=11 forever until we have infinite diamonds. That's how it's always been as long as anyone can remember.

All that has suddenly changed. It's gone, it's out the window forever. And it's about bloody time.

It's one thing trying to preserve a game for nostalgia, but it's got to change eventually. Minecraft's evolution is arguably why the game is still so relevant in its 12th year of life. The game has constantly evolved and grown over the years, but until recently, the core progression has remained almost unchanged for years. It's finally time for change. The days of mining an endless tunnel exactly 52 blocks below sea level are done.

Doubling the underground is something I had been wishing for since 2012. From about the time I had been playing for all of 2 months, I had always found the vertical progression underground incredibly lacking. The surface never felt too far away, and as a result, caving never really felt too dangerous or exciting. Spelunking at y=-50 genuinely feels pretty terrifying, knowing that I am more than 100 blocks underground, and that should I run into danger or run out of resources, or get lost, I am a LONG way from the surface and a LONG way from safety!

This is absolutely groundbreaking. It makes a player of 8.5 years feel excited to play Minecraft again! It is a genuinely new and novel experience to the most downtrodden part of the Minecraft experience!!

With the size of the caves and how dark they are, the spyglass and night vision potion will actually be useful now!

Speculation

Now, it is worth noting that this is just the beginning. This is step ONE of the "caves" part of Caves and Cliffs. We don't yet have the new biomes, and we don't yet have the Deep Dark. Ores have yet to be balanced too, making diamonds incredibly abundant below y=0. The devs have confirmed the ore placement is subject to change, so I'm not too fussed about that.

What is interesting, however, is where the Deep Dark will come into all this. I reckon the other biomes will "intersect" with the new noise caves, such that you get small lush caves and massive lush caves. Small dripstones, large dripstones. The Deep Dark, however, remains a complete mystery. 

I have two thoughts on the Deep Dark: one is that below a certain y-level, say Y=-32 or so, the stone changes to the deep dark stone we saw in Live, and the biome transitions to Deep Dark. It could be that below this level, the light works differently (going in and out like we saw in the trailer), and maybe even that to mine this new stone you need a certain tier pickaxe higher than wood. Any caves sub y=-32 become Deep Dark caves. Maybe down this far you can find more ores than before, who knows. My other thought is that like other biomes, the Deep Dark will only appear in patches, but only below a certain y-level. Anything in "deep dark" region above y=-32 is just normal stone/cave.

Either way, I am very excited to see how Mojang implement the Deep Dark, which has always been one of 1.17's most mysterious features. But now that they have doubled the underground, it is a lot more clear how it could fit than before.

Also, unrelated to the caves, but with the extended underground, this could also mean deeper oceans could be implemented. Maybe some sort of "Super Deep Ocean" that extends all the way down to y=0. SO much is possible with this incredible change!

Critique

So I've had 3 days to play around with the new caves, and of course - if every porkchop were perfect, we wouldn't have hot dogs. (If you get this reference, let's be friends!) There ARE a couple of issues that I'm sure will be addressed, as this is just the first iteration of the new caves. 

Three words: Diorite, Andesite, Granite.

These have always been three of my least favourite blocks in the game, and now their appearance in the new caves is... well... a bit hideous. I am sure Mojang will come up with a way to mitigate this. Maybe instead of having these blobs of these three stone types, we could even get entire caves that are made of andesite, granite and diorite. I have also always wondered why these blocks don't have ore variants. I mean, back in the day there was a block limit so that was understandable. But now, when we have like 40 different copper block weathered/waxed/cut/stairs combinations, why not have ores embedded in diorite, andesite and granite? Maybe even have it so that iron ore is found in all stones except granite, so if you want to find iron, don't look in a granite cave. This is another way Mojang could add strategy to mining.

As it is the first iteration of these new caves, some underground structures such as geodes, dungeons and strongholds also need adapting. But seeing the wonderful ways they've adapted the mineshaft gives me a lot of hope for how they will adapt these other old structures!

And finally, the sheer size of the caves does to a degree actually take away some of the difficulty when it comes to mobs. Some of the biggest caves are SO massive it's like being on the surface (other than it being really really dark). This means you can outsprint mobs - whereas before this was much harder in the tight narrow caves. That being said, as it is so dark you might accidentally jump off a massive drop and fall to your death whilst running away. So swings and roundabouts I guess!

Final Word

It is rare that a snapshot drops that well and truly blows my socks off. A snapshot includes a change or a set of changes so monumental it feels like I'm playing a different game in all the best possible ways. Rather - a MUCH better version of the Minecraft I've come to know and love. Like a mod that makes Minecraft even better - except it's in vanilla. The first 1.16 snapshot and to some degree the snapshot that added the Basalt Deltas were perhaps the last example of this. But this snapshot is a fundamental paradigm shift to the EARLY game - and finally after many years, we have a MUCH needed shake-up to the formula. I know lots of others have said this, and it's really cheesy but.... they have finally put the "mine" back into Minecraft.