D01: Christmas lights with Arduino

D02: Automatic street light circuit

D03: Center of mass of a rod

D04: Center of mass of a circular arc

D05: Center of mass of a roly-poly

D06: An interesting friction effect

D07: Magnetic braking

D08: Atmospheric pressure

D09: Magnetic train

D10: Stable vertical motor

D11: My 2D balancing eagle

D12: Refraction of light

D13: Gravity versus air drag

D14: A polemeter!!!

D15: Styrofoam cutter

D16: My hovercraft​

D17: Slow down, my friends!

D18: Less resistance, more light

D19: An electromagnet

D20: My old 3D-printed friend

D21: I saw more than just sponges