Astro Boy Rescue

In each of the four levels, Astro Boy had to rescue his friends one by one. To do this, he grabbed colored spheres and dropped them onto matching ones below. When four or more spheres of the same color lined up, they vanished in a satisfying pop. Clear the screen, save a friend, move on: simple yet effective. 

Source: https://mixture.ch/projects/astroboy/index.html