Casino Night Zone is a location in the Sonic the Hedgehog series which was first introduced in Sonic the Hedgehog 2. It is a casino-themed city Zone, geographically located somewhere on West Side Island. While it is never stated if Dr. Eggman is the one behind constructing Casino Night Zone, it is possible that this zone was built by somebody other than him. The city is always seen set during the night time with jaunty electric colors. Casino Night Zone features a pinball-based level design with many known gimmicks such as bumpers, pinball flippers and slot machines.
Casino Night Zone has made the Casino-themed Zone trope iconic in the Sonic the Hedgehog series and has made multiple appearances throughout the games, while many later games have various Zones based of it. Casino Night Zone is also featured as a racetrack in Sonic Drift 2, as well as a returning stage in Sonic Generations as a pinball minigame DLC on the console versions and representing Sonic the Hedgehog 2 as a stage on the 3DS version.
Sonic the Hedgehog 2
Making first appearance in Sonic the Hedgehog 2, Casino Night Zone is the fourth Zone in the game, coming after Aquatic Ruin and before Hill Top. The level design is somewhat different and more pinball-table based, with neon colors. The Zone introduces to the slot machines gimmicks in the series, where the player can rack up hundreds of rings should fortune be on the player's side to get the right combinations. Many other gimmicks include bumpers, pinball shooters and flippers. As with most other stages in this game, Casino Night Zone consists of two standard Acts with a boss fight at the end of Act 2. Casino Night Zone is most notable for hardily containing any enemies but has a single bumper enemy per Act.
Sonic Drift 2
Sonic and friends re-enter the "pinball paradise" during the 2nd Chaos Grand Prix in Sonic Drift 2. Casino Night is the fourth track of the Purple Grand Prix (Purple being the easiest of the three available tournaments), coming after Dark Valley 1 and before Desert Road 1. As with most other races in the 2nd Chaos Grand Prix, you have to complete three laps of the track to finish, and the fastest racer gets a Chaos Emerald.
Casino Night's track is littered with oddities; mini ramps that throw you up in the air, springs that aren't really springs (they're actually bumpers), and the strange reverse-spheres (later seen in Iron Ruin) that invert your controls. Most of the time, there is at least land on either side of the track, although there is one section where this is replaced by empty space - so you don't want to fall off.
Sonic the Fighters
Casino Night appears in the arcade game, Sonic the Fighters. It's the arena where the player faces Fang the Sniper. If the player is playing as Fang, Dr. Eggman will swoop in and make a clone of him. After they defeat him, the player gains a magenta Chaos Emerald. The arena features many neon lights including one that resembles an emerald in the middle. The bars on the arena are neon versions of playing cards. The background features a roulette wheel and a slot machine that never seems to stop.
In celebration of Sonic's 20th anniversary, Casino Night reappears in Sonic Generations. It is a full level on the 3DS version, but it is a downloadable pinball mini-game in the console/PC version. It is only one of two levels (Green Hill being the other) to appear in both the console and handheld versions of the game. Classic's Act is the exact level layout as Act 1 of the original, except that the Speed Shoes in this level are replaced by Ring Monitors.
In other media
Adventures of Sonic the Hedgehog
A new Casino Night Zone appears in the episodes "High Stakes Sonic" and "The Mobius 5000". In "High Stakes Sonic" it appears to look like an oversized casino, and is hooked up to a CPU designed to force every machine in the house to lose no matter what. When Sonic reprograms the unit, this causes the Mobians inside to win real money (due to Grounder not wanting to welch on a bet) and bankrupts the casino. There also appears to be a nursery where Tails gets caught, and a large athletic arena where Sonic races Grounder.
Sonic the Comic
In the Sonic the Comic series published by Fleetway Editions, the Casino Night Zone is one of the many Zones on Planet Mobius. It is a large, urban region, devoted entirely to the leisure industry (especially casinos). At first, the Zone was ruled by Dr. Robotnik, but the money-greedy Max Gamble eventually became its de-factor administrator. Since its introduction, it has held a strong element of illegal activities.