I find it hard to believe that 15 years ago today, Sonic Adventure 2 was released on the Sega Dreamcast. As someone who grew up with the 3D Sonic games, Sonic Heroes, Sonic Adventure 2: Battle (the GCN port), and Shadow the Hedgehog were among my favorite games. Looking back now, they definitely had their flaws. However, they were beyond entertaining for me as a child and I've grown to discover the deeper story the games have to offer. So, let's take a look back on what Sonic Adventure 2 had to offer:
A Split Narrative
Continuing on the idea established in Sonic Adventure, this game offers a split narrative that gets slowly built between the "Hero" and "Dark" stories. Both stories are complete in their own right and occasionally crossover in the form of boss battles to give an insight into the events of the parallel story. Each level also comes with a briefing from the character you assume for that level to catch the player up on the events of the story up to that point. This concept is further expanded in Sonic Heroes which was released a few years later.
My favorite aspect of these stories is the growth of the characters in the "Dark" story. The characters are not purely bent on their evil intentions, but capable of showing growth. I've always loved Shadow especially because of how deep a character he is. His motives are driven somewhere between a desire for power and a need to enact revenge, but he is still willing to compromise for the sake of helping someone important to him. These ideas get explored more heavily in Shadow the Hedgehog which provides my favorite Sonic narrative of all. In much the same way, Rouge has her own motives that sometimes lead her to align herself with the likes of Eggman if only to further herself along. Yet, the interactions between her and Knuckles in this game seek to "humanize" her in a way.
Differing Level Structure
Continuing on the story structure idea, each level was created around a different character and specifically tailored for that character's story arc. Sonic and Shadow have levels that focus on speed and cool tricks. Their stories follow their respective attempts to stop the other at every corner. Tails and Eggman's levels are more tactically based with fighting enemies in a "bullet hell" environment which necessitates a health bar for these characters. Their stories involve setting into motion plans to save or dominate the world as the case may be. Knuckles and Rouge's levels involve treasure hunting as is their nature. You follow a radar to find the location of chaos emeralds and master emerald shards. This presents the most interesting mode to me because the levels are more free-roam based and are completely different from the rest of the game. They also further solidify the idea that Knuckles and Rouge are so focused on their own motives that they operate outside of the goals of those around them. Sure, Knuckles is a hero and Rouge is a government agent, but both are ultimately concerned with finding the treasure that they value.
The Chao Garden
Arguably the best part of the game, and definitely the most adorable, is the Chao Garden. If you're not familiar, the Chao Garden is a hub world within Sonic Adventure 2 where you can raise and train your own adorable little creatures. Each level has little animals and colored tubes to collect which provide stat boosts to Chao upon receiving them. Giving an animal to a Chao will change the physical appearance of a Chao as will their encounters with "Dark" and "Hero" characters.
There are multiple sections to the Chao Garden, though: the School, the Gardens, and the Minigames.
The School is a location where you can take your Chao to help it learn like a regular child. You can also have it evaluated by the school Doctor to see which stats it excels in and which ones it falters in. This takes on a weird aspect of Chao breeding that can effect your Chao's performance in Minigames. However, you're given plenty of Chao to work with and if you put the effort in, you may come out with a perfect Chao.
There are also multiple Chao Gardens to run around in. The Chao Garden is the starting Garden wherein you get your starting two Chao which can be influenced by "Hero" and "Dark" characters until it transforms into either a Hero or Evil Chao. Once a Chao has undergone this transformation, you unlock the Hero or Evil Chao Garden depending on the transformation. The Evil Chao Garden is pictured above and both gardens come with a new Chao egg (the Chao being already evolved depending on which garden it's in).
Lastly, there is a Minigame section where you can take your Chao and have them compete in competitions. These competitions include various relay races that test their skills (flight, stamina, speed, etc) or martial arts competitions akin to the most adorable Mortal Kombat matches you've ever witnessed. Both of these competitions are completed by the AI and your only influence is how they use their stamina in the relay races.
Even after all these years, there's still one aspect of the game that I don't think I'll ever forget: The first song. If I remember right, I'd always want to play that first Sonic level just for this song (you know, before YouTube was a thing). So, enjoy that song that'll probably get stuck in your head all over again!