Season 2

8x8
Writing in Place: 8x8 LED Matrix Modules It's a key piece of the placemaking puzzle: the ability to write text in place -- out in the world.  And it turns out there's a standard building block for the kind of grid you can use to make it happen: the 8x8 LED Matrix -- 64 LEDs in a square, controlled by a commodity chip: the MAX7219, or some minor variant.  They are available on Alibaba, in bulk, for around 90 cents apiece.   And they are modular: you can buy them chained together, in blocks of 4, for less than $4. Just search for "4-in-1 LED Dot Matrix Display Module." That's what you did. 

version #2 in acrylic
Mixed Reality Gumball Machine: Version 2 Your Mixed Reality Gumball Machine works, most of the time. Sometimes you have to enter the secret password twice to get one prize; other times you get two prizes.  Sometimes you can see, and hear, some jostling around inside the gumball dome, but nothing comes down the chute.  The top level of plastic gumball containers roil a little bit, like something is stirring in the underlying layers, but no prize emerges.  There is an element of chance, sure, but not in a good way.  You wanted something SOLID, reliable. So planning begins on Version 2. 

stepper
Stepper v Servo The difference is about the poles.  A pole is an area of a motor where a North or South magnetic pole is generated either by a permanet magnet or by passing current through the coils of a winding. Servos have between 4 and 12 poles. Stepper motors have between 50 and a hundred.  Steppers don't require encoders since they can accurately move between their many poles. Whereas servos, with few poles, require an encoder to keep track of their position. Steppers simply move incrementally using pulses, while servo's read the difference between the motors encoder and the commanded position, and adjust the current required to move.