I personally have a history of following my younger brother of 3 years into games I've never played before. He's the new game trailgazer, I'm just his follower. This was the case when he found a little game called Minecraft in 2010 (you may have heard of it), and I played that game to death... but in a repetitive, peaceful way. That drags on you if you do that for a year and a bit without any direction.
I had noticed that I always seemed to follow into whatever games my brother was playing, and told myself that the next time I was tempted, I would not follow him again.
Cut forward to late 2011. I saw my brother was playing this new 2D game. I made the obligatory "is this a 2D Minecraft?" line, and continued watching my brother play this fascinating game, while also telling myself "I'm not going to play this because that would be following him again."
It didn't take me too long to give in, and try it out for myself. (I never said I was very resolute in my decisions.

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This was in the era of the 1.0 updates, and for me, it was during 1.0.6.1. Every day I could get a new piece of better iron, silver or gold armor was an accomplishment. I had heard about this very hard boss in the purple biome to the right of my house, and was determined to be as geared as possible to take him on. So, with full gold armor, the best weapons I had, and some buff potions, I went and smashed 3 Shadow Orbs, and took on the beast. Actually, I was so well equipped, that the Eater of Worlds was laughably easy. Oh well, onwards with progression!
It was around this time that I absorbed the wiki for as many details as possible. I found all kinds of information that I had not known before, like that this "Skeletron" thing I had heard about wasn't just someone mistyping/misreading the word "skeleton". And since I had no clue that the forums existed at this point, I had no idea that some entries in the wiki might have been pertaining to an upcoming patch that had not arrived yet, because I remember reading on entry on Corruptors, while having no clue why this "Wall of Flesh" wasn't appearing when I chucked a guide voodoo doll into lava. A quick double check of the wiki told me that I was rushing things a bit.
And then, it happened. 1.1 hit, bringing a nice graphical update to the background layers, HARDMODE, and the Sun became less orange. Rip 1.0 Sun.
Given my history with making world upon world in Minecraft for each new update, I decided to skip that for this game, and stick with my original 1.0.6.1 world for the whole duration of 1.1, for this original playthrough, anyway. I looted the dungeon, got poisoned by the jungle, and made my ultimate weapon, the Night's Edge. I was super proud of this thing... and wouldn't get rid of it until much later... but I'm getting ahead of myself.
I through the guide voodoo doll in the lava, and defeated the Wall of Flesh for the first time. I'd have to go and look at the world again, but I think I defeated him without a hellbridge...? Truly, I was a madman if that is the case.
Now I had the Corruption to the immediate left of my house, and the Hallow to the immediate right. Plus, the tunnels I used to get to hell (I never made a Hellavator in this world... TRULY a madman) were infested with these two biomes almost all the way down. Especially for my prehardmode player, this was a rough start, and after some altar smashing and dying the wraith spam, made it a challenge to go and get the resources necessary for gear upgrades.
Because I had devoured the wiki, I knew that ultimate challenge lay ahead of me - the Mech bosses. I aimed to get as much Adamantite gear as possible (I called it Adamanite at this time because apparently I can't read). Because my primary weapon was always a sword at this point, I crafted an Adamantite Sword ahead of Adamantite armor... but still held on to my Night's Edge, because at this time, a Legendary Night's Edge still did more damage than my Godly Adamantite Sword, but did considerably less knockback.
Fast forward a bit to after I finally acquired full melee Adamantite Armor. I was feeling pretty good about myself, and as a result, decided to take on the Destroyer, which was apparently the recommended boss to take down first. Yeah... that didn't go to plan, and I died pretty early on in the fight. So I went for Plan B, and decided to take on the Twins with a trusty Clockwork Assault Rifle I had lying around in a chest. And... I won, but it was close. The 1.1 Mech bosses are probably the hardest version of the bosses due to the lack of extra utility options that the modern versions give you (like campfires, heart lanterns, etc.) I was super stoked at this, cause it meant I had access to one of 3 different boss souls, and I immediately crafted the Hallowed Mask.
Turns out, that was a bad idea... because I was ignoring the decent armor set bonus of Adamantite by doing that... I trying to take on the Twins again after that resulted in failure after failure. I was pretty ticked off by this, as you can probably imagine, as I had already beaten this boss once before... granted, only by the skin of teeth. So the lack of the set bonus meant that I kept losing every time. So back underground I went to go and track down even more Adamantite ore for a second Adamantite Helmet.
New helmet in tow, I finally defeated the Twins a second time, and crafted the Magical Harp. Turns out this thing was (and probably still is) OP against the Destroyer. Find a spot to aim straight down his body, and he melted like an icecream. And just like that, I had access to the second boss soul, which was promptly crafted into a Megashark, as I heard that this weapon was pretty crazy powerful.
No kidding, as not long after crafting it, I took on Skeletron Prime, and after maybe a failed attempt or two, I prevailed! Finally, with all the bosses taken down at least once, I could focus on getting a full set of Hallowed Armor, and every single piece of Hallowed gear, since back in the day, there was no such thing as Hallowed Bars... all Hallowed gear pieces were crafted with boss souls and the Cobalt, Mythril and Adamantite equivalent of that gear piece. No small feat.
So many, many bosses defeated later, I was on top of the world! I had a character with pretty much the best gear in the game, and so I could pretty much anything I wanted! Like remove half of a generated Corruption biome by hand because I felt like it, and the other half was already Hallow, so might as well finish it off. (Granted, I did this before I got my hands on a Hamdrax, so this was slower than one might expect.)
That pretty much wraps it up for my first playthrough of the game. I think it took me from late 2011 to mid 2012 to finally get from start to finish. Oh man, the nostalgia is real.