The first Sinclair item I had was in the mid 1970's - a Sinclair Radionics kit which had a multi-purpose circuit board along with various electronic components mounted onto bits of plastic, along with a manual full of different wiring positions telling you what positions to bolt the various components into, to make at least 40 different circuits such as a radio transmitter, tone generator, burglar alarm. I'm sure playing with that helped me get a C in my 0-level Electronics (everyone else in the class failed).
I got a ZX81 and was very proud of managing to code a working version of Pong in under 1K of memory by using the CODE function in Basic which saved a few bytes of space for each line.
I still remember the pain and anguish caused by the dodgy contacts on the later 16K memory expansion pack, when you lost everything.
