Sonic Adventure

Sonic Adventure is a 3D platform game with action and role-playing elements. Players control one of six anthropomorphic protagonists as they venture to defeat Doctor Robotnik and his robot army, who seeks the seven Chaos Emeralds and the entity Chaos. Six player characters are unlocked as the game progresses, each with their own story and attributes. Sonic the Hedgehog performs a spin dash, homing attack, and light-speed dash; Miles "Tails" Prower flies, swims, and attacks robots using his tails; Knuckles the Echidna glides, climbs walls, and punches; Amy Rose can defeat enemies using her hammer; Big the Cat is slow and carries a fishing rod he can cast; and E-102 Gamma can shoot laser beams.

At the start of the game, the player is placed in one of three Adventure Fields, open-ended hub worlds inhabited by advice-giving NPCs. The player is guided and instructed by the voice of Tikal the Echidna. Through exploration, the player discovers entrances to levels called Action Stages, some of which must be opened using keys hidden in the Adventure Field. Once the player accesses an Action Stage, they are tasked with a specific objective, which is different for each character. Sonic must reach the level's end similarly to prior Sonic the Hedgehog games; Tails must reach the end before Sonic; Knuckles must find three hidden shards of the Master Emerald; Amy must solve puzzles and avoid being caught by a robot; Big must fish for his pet frog; and Gamma must fight his way through stages using projectiles as a defense.

The mad scientist Doctor Robotnik seeks a new way to defeat his nemesis, Sonic, and conquer the world. He learns about Chaos, a creature that, thousands of years ago, helped to protect the Chao and the all-powerful Master Emerald, which balances the power of the seven Chaos Emeralds. When a tribe of echidnas sought to steal the power of the Emeralds, breaking the harmony they had with the Chao, Chaos retaliated by using the Emeralds' power to transform into a monstrous beast, Perfect Chaos, and wipe them out. Tikal, a young echidna who befriended Chaos, imprisoned it in the Master Emerald along with herself. Robotnik shatters the Master Emerald to release Chaos and tests its natural form on the city of Station Square.

After police fail to defeat Chaos, Sonic and Tails work to stop Robotnik from empowering it with the Chaos Emeralds. Knuckles, the only remaining echidna, sets out to find the shards of the Master Emerald. Robotnik activates a new series of robots, including E-102 Gamma, and orders them to find Froggy, a frog who ate a Chaos Emerald; Froggy's owner, Big, seeks him as well. Back in Station Square, Sonic's friend Amy protects a Flicky being pursued for its Chaos Emerald.

During the early 1990s, Sega was one of the most successful video game companies due to the rise of its Genesis console. Genesis sales were driven by the popularity of Sega's flagship franchise of 2D platform games, Sonic the Hedgehog. During this time, series co-creator Yuji Naka worked with Sega Technical Institute (STI) in the United States to develop Sonic games. After the completion of Sonic & Knuckles in 1994, Naka returned to Japan to work with Sonic Team.

STI began developing Sonic X-treme for the Sega Saturn, planned as the first Sonic the Hedgehog game to feature full 3D gameplay. X-treme suffered a series of setbacks and was canceled in 1996. The cancellation was an important factor in the Saturn's commercial failure, leaving it with no original Sonic platform game. Meanwhile, Naka and Sonic Team developed original Saturn games, such as Nights into Dreams (1996).

As the first fully 3D Sonic platform game, Sonic Adventure was highly anticipated. It received critical acclaim, and Computer and Video Games (CVG) called it one of the greatest video games of all time. Sonic Adventure won a Blockbuster Entertainment Award in the "Favorite Sega Dreamcast Game" category, and was a runner-up for GameSpot's annual "Best Console Platform Game" award, which went to Rayman 2: The Great Escape (1999). It was a finalist for "Outstanding Achievement in Visual Engineering" during the 3rd Annual Interactive Achievement Awards, which went to Unreal Tournament.

The visuals and presentation attracted acclaim. Arcade described it as a "quantum leap forward" in aesthetics and visual detail in video games, and Hyper estimated it exceeded graphics of high-end personal computers. Brandon Justice of IGN called it the most graphically impressive platform game released up to that date, praising its cinematic sequences and describing it as "engrossing, demanding, and utterly awe-inspiring". Peter Bartholow of GameSpot agreed and said only Soulcalibur's graphical quality surpassed it.

With most contemporary 3D platform games focusing on exploration and collecting items, Sonic Adventure stood out with its linear gameplay. According to GamesRadar, as one of the first sixth-generation console games, it changed the industry "forever". Joystiq wrote that both Adventure and the original Sonic the Hedgehog had innovated in 3D and 2D through effective linear level design and by feeling "good to play".

In 2009, GamePro listed Sonic Adventure as the seventh-best platform game, saying that it had not aged well in certain aspects but that its core gameplay remained among the best of the Sonic series. Several journalists ranked the game among the series's best, but Kotaku argued the addition of voice acting and greater focus on plot changed Sonic into "a flat, lifeless husk of a character, who spits out slogans and generally has only one personality mode, the radical attitude dude, the sad recycled image of vague '90s cultural concept".