This is four arcade buttons and four smart full-color LEDs, drilled into an IKEA Antilop high chair (a spare tray is $5). The brain is a 5v Adafruit Pro Trinket, powered by four AA batteries.
The default mode is the same as the blinky my dad made for me long ago: press the red button and the red light lights up, press the green button and the green light lights up, and so on.
Holding down all the buttons at once lets you switch modes: mode two is like mode one, except each light stays on until the next one is pressed. Mode three is like a typewriter, and mode four is a step sequencer.