Yoshi's Universal Gravitation (released as Yoshi Topsy-Turvy in the USA) is a Puzzle Platformer in the Yoshi series, developed by Artoon and released in 2004 for the Game Boy Advance (2005 internationally).
Bowser has been rampaging across Yoshi's Island, sending the peaceful land into disarray. Fortunately, Hongo, the well-intentioned ruler of a spirit-filled tome known as the Forbidden Pop-Up Book, takes it upon himself to seal the evil Koopa King within the book's pages. Unfortunately, the entirety of Yoshi's Island is sealed along with him! It's up to Yoshi to defeat Bowser, hopefully convincing Hongo to release his homeland from inside the tome. And this time, he wields the power of gravity.
The game features six different worlds, or "tales" (eight if you count two boss-only worlds), each of which introduces a different spirit from the Forbidden Pop-Up Book. The levels follow a mission-based structure, in which, apart from completing the level, you must do it in the way the level's spirit host desires. Each spirit has their own particular theme and desires, and in later worlds, levels can be hosted by two spirits at once! If you satisfy the spirits, you will receive a Happiness Medal, a number of which are required to progress.
In the vein of Kirby Tilt 'n' Tumble or WarioWare: Twisted!, the gameplay hinges around a gyroscopic tilt sensor built into the game's cartridge. By tilting your Game Boy Advance around, you can help Yoshi advance through the various levels in multiple ways.
Yoshi's Universal Gravitation provides examples of:
- Advancing Wall of Doom: The Spirit of Fright's levels work like this. He places a rolling spindle with spikes in the level that never stops advancing and you must outrun.
- Affably Evil: Or affably antagonistic, at least. The Spirit of Fright is polite in face-to-face conversation with Yoshi, but he's the only spirit that actively tries to harm or hinder him by placing continuously advancing rolling spikes on his levels.
- Band Land: The entire game has a not excessively prominent, but noticeably recurring musical theme. In particular, the ball objects found in a number of levels are called Chime Balls and noticeably have a picture of a treble on them. If you roll these balls over xylophones that are found on the ground in certain areas, they will produce musical notes that can be used as platforms.
- Big Good: Hongo, the benevolent leader of the book spirits. Ironically, the reason the plot is set in motion is partially his fault, since it is him who seals the entirety of Yoshi's Island in order to stop Bowser. He's also implied to have something of a temper. In any case, he still qualifies, as he ultimately has the people's overall best interests at heart, and in the ending, once Bowser is defeated, not only does he release Yoshi's Island, he readmits the Spirit Who Loves Surprises.
- Boisterous Bruiser: The Spirit of Power, a large and portly Djinn-like spirit who believes Might Makes Right and is quite loud.
- Cash Gate: The Spirit of Greed missions require you to collect a certain number of coins if you want to win a Happiness Medal.
- Collection Sidequest: The Spirit of Cuteness' levels feature this. Yoshi must collect egg-like creatures known as Egglings, who have been turned into apples by Bowser and can be rescued by eating them. There's a hundred of them, and they have different sizes, designs, and even names. The game provides you with an "Eggling Book" that you can consult in order to see the Egglings you have rescued.
- Gasshole: Yoshi's iconic ability to turn the enemies he eats into eggs that he later can throw is not present in this game. He can still eat enemies, but instead of laying an egg he will produce a small puff of air. The egg throw was probably unimplemented because the game already has enough gameplay gimmicks as is.
- Gone Horribly Right: Played for Laughs. In the introduction, after the Spirit Who Loves Surprises gives Yoshi the power to control gravity, he asks him to test it. This leads to Yoshi accidentally (In-Universe, very deliberately out of universe) making a rolling ball crash into him, sending him flying.
- Gravity Master: Yoshi becomes one of these In-Universe in this game. Out of universe, this serves as a justification for the game's tilt-based gimmick. By tilting the console, the player can affect the game levels in many ways, such as making balls roll or unrolling bridges.
- Greed: There is a Spirit of Greed, who is evidently an embodiment of this. He values gold and riches above anything, and has a pouch where he carries a large number of coins and gold bars. Even his shadow is gold.
- Egg McGuffin: The Egglings are cute little egg creatures that have been magically turned into apples and you must rescue.
- Helpful Mook: A number of these appear. Fat Guys can be used as a trampoline to reach tall places, Goonies can be ridden in order to reach otherwise unaccessible areas, and Igashira-kuns (spiked enemies introduced in this game, not too dissimilar from the Gordo enemies in the Kirby series) can be rolled into other enemies by tilting.
- Invincible Minor Minion: Such an enemy appears in the sixth world. Their English names are unknown, but a Japanese guide gives it as "Daruma Otoshi-kun". They are walking bird-like enemies with spiked backs that cannot be defeated in any way. The Fat Guy is also undefeatable in this game.
- Jerk with a Heart of Gold: The Spirit of Kindness has an attitude resembling The Diva or an Alpha Bitch, but true to her name, she tasks you with killing as few enemies as you can.
- Hyper-Destructive Bouncing Ball: The Ball Yoshi transformation is this. Yoshi becomes a bouncy ball that is completely invincible and can smash through walls, and is only controllable by tilting. Particularly in level 4-4, Yoshi spends the entire stage in this form.
- Kill 'Em All!: In his missions, The Spirit of Power asks you to go out of your way to defeat a set number of enemies of his choice.
- Non-Ironic Clown: The Spirit Who Loves Surprises looks very much like a clown or jester. He's also the nicest and most helpful character you meet in the game. It is him who gifts Yoshi the power of tilting and, unlike the other spirits, asks nothing in return. He even tried to convince Hongo to not seal Yoshi's Island within the Pop-Up Book, leading to him getting fired.
- Pacifist Run: Contrasting with the Spirit of Power, the Spirit of Kindness requires in her missions that you defeat as little enemies as possible, only four at most. This can be a bit of a headache, as the enemies certainly like to get in the way. Killing no mooks at all will get you a gold Happiness Medal.
- Rank Inflation: Downplayed. The levels have two different requirements that you can fulfill in order to get a Happiness Medal, one of which being easier to achieve than the other. Both of them net you a Happiness Medal, but fulfilling the harder requirement will get you a gold one, while settling for the easier one will make it silver. Of course, failing both of the requirements will get you no medal and you will have to retry.
- Ridiculously Cute Critter: Not only the Egglings, which are egg creatures with dot eyes, but also the Spirit of Cuteness herself, who is pink, round, and has a wide rosy-cheeked smile.
- Secret Test: In the end of the first boss battle against Bowser it is revealed that it wasn't Bowser at all! Rather, it was a puppet being manipulated by the Spirit Who Loves Surprises in order to test Yoshi.
- Selective Gravity: Despite being such a heavily gravity-based game, Ravens are still immune to it and will often be happily seen walking on walls, so watch out for them!
- Time Trial: The Spirit of Speed asks you to complete her levels in a set amount of time.
- 20 Minutes into the Future: The game is set in this when compared to the rest of the Yoshi franchise, as evidenced by the presence of an adult Bowser. This actually means that it's set in the Present Day relative to the wider Super Mario Bros. franchise, since the other games are set 20 Minutes into the Past.
- Underground Monkey: In the final battle, Bowser can summon a rainbow variation of the common series enemy Tap-Tap. This particular version, however, only appears at this point of the game, and has not appeared before or since.
- Under the Sea: Not under the sea in this case, but there are a number of watery areas where Yoshi will be transformed into Ship Yoshi or Boat Yoshi and float above the water. By tilting the console you can make the water level change, which is often necessary to reach objects and places or avoid obstacles.