Love Lab (恋の実験室,Koi no Jikken-Shitsu?, "Laboratory of Love") is the 19th minigame of Rhythm Heaven. The playable character is a scientist student who has a crush on her senior lab partner, and she, her senior partner and another student are conducting an experiment about the science of love. When getting a perfect, the gift "Lab Journal" will be available to read in the Café.
The male scientist student gets a flask tossed to him. He will shake the flask a number of times and toss it to the female student (the character played in the game). The flask must then be shaken the same number of times he shook it by relying on the tone of rhythm in the game. The player then must toss the flask to the other student in the lab. If the flask was shaken correctly and in time, all of the hearts made by both students will be combined and fall into the white bag.
Hold down stylus: Grasp flask
Slide: Shake flask
Flick: Toss flask
Hit: The flask is successfully grabbed, shaken and then tossed to another scientist. The hearts will combine and fall into the white bag.
Barely: Grabbing the flask too early or too late will result in a heart either not coming out or floating away. A barely counts as a miss.
Miss: The flask is not grabbed nor tossed, instead falling onto the counter and breaking into pieces. If the player holds the flask and does nothing, or shakes off beat, their hearts will not combine with the senior lab partner's hearts and float away instead. The senior's hearts, if left uncombined, will dissipate into skull shaped vapors.
This game takes place in the daytime during the practice and Remix 10, and at sunset during the real game. The game shares this trait with Double Date. Both time settings are used in Remix 4.
The guy in the costume has a full sprite, but most of it remains off-screen.
The Hearts that come out of the flasks also tell you wether you were early or late. If it's a bit over the heart produced by your partner on the left, you grabbed/shook the flask early. If lower, you were too late. If it's right where the heart/hearts are before, you hit it just right.
There is a different opening banner in the Japanese version featuring an AIAIgasa (相合傘) which is the act of sharing an umbrella that can be considered romantic in Japanese culture. whereas the International versions had pink and blue abstract text spelling "Love Lab" along with a blue flask moving to the center in a choppy way,