Built to Scale (組み立て,Assembly?) is the first game in Rhythm Heaven. It features recurring Widgets in which you must shoot rods through them during the mass-produce line. Getting a perfect unlocks the Built to Scale soundtrack. The sequel, Built to Scale 2, is unlocked later on.
The player shoots a rod through the center of the squares that pass by each other. To rhythmically succeed in this game, the player must follow the pattern "do-re-mi-fa-sol" with the music, flicking on "sol". Amid the level, the screen becomes dark except for the middle and the game becomes somewhat increasingly difficult. This part of the level forces the user to use the audio to win, as well as their rhythm rather than relying and seeing when the widgets align.
Flick: Shoot Rod
Hit: The rod hits both squares and connects them.
Barely: The rod will hit both squares, but knock them down, only sending the rod itself down the conveyor belt (Barely counts as a miss).
Miss: The rod and squares never make contact, and the squares will roll into the nearby slots and disappear through them.