Oh dear! Another alarm system!
Why do I presume to inflict this announcement on you?
I hope this one is “different”!
It is complete. It comes with a tutorial about programming, not just raw code for you to make what you can of. It is something in actual use… for some time… not a bit of rambling about things which “could” be done.
(When I say “in use”… I use a functionally equivalent system. I wrote the Arduino equivalent as the original runs in a PC, using DOS, and a program written with Turbo Pascal. I was in the position of knowing that if that were to fail tomorrow, I would have to scramble. Now I have a replacement ready.)
I think the system achieves a good balance between being simple and being capable.
You will find something useful in the web page… I hope!!!