get an ESP32, costs about $1-3

you can program it with the USB and the Arduino IDE

most dev boards (that means the MCU is put onto a PCB and you can do stuff with its pins) already have a LED on it so you can blink that without any soldering

they also usually have two tiny buttons one of which doesn't do anything/much and you can use those as input

ESP32 also has built in Wifi and you can make it host a supertiny webserver, or even be its own AP. It also has Bluetooth but I haven't tried that yet.

You can do all these things by asking ChatGPT for the code and instructions :-)

It can do a lot more than this though, but it might inspire you to try other things.

Oh one more very cool thing if you're just getting started is that the ESP32 has 10 pins which are "capacitive touch" sensors and attach a wire to that pin and if you touch the wire, your program gets a signal. This works very well and makes that you can do interactive stuff without even having to solder buttons on anything.