An explanation of the internal structure of seven-segment displays in both types (common cathode and common anode) and how to wire them to Arduino.
An explanation of how a standalone joystick module works internally and wiring it manually to Arduino with five pins.
Mounting the Joystick Shield v2.4 directly onto Arduino, and its components — two analog axes and seven digital buttons.
Building an automatic irrigation system that opens a solenoid valve when soil is dry using the FC-28 sensor and a switching transistor, with a safety note on the protection diode.