I rewrote the whole thing and added GUI and some basic features. I named this app "SMAC". This is basic mouse auto-clicker now. You can download it from:
https://pastebin.com/bu1b73nk
Press "Download" and rename
smac v.2.08 src.ahk.txt
to
smac v.2.08 src.ahk
(I can't attach .exe binaries here, as steam wont allow it. So you will have to run raw .ahk script).


You will need to install AutoHotkey and run smac v.2.08 src.ahk after that:
1) download and install AutoHotKey (during install, if asked answer yes for .ahk extension association).
2) Open "smac v.2.08 src.ahk" file.


It looks like this:

The lower (closer to 0) the first delay is - the faster the auto-clicking will be. The second delay creates pause between each auto-click.
The fastest auto-clicking speed is 0ms/0ms combo. But 10ms/0ms (10-first delay / 0-second) is more reccomended. Just don't use first delay more that 10 - it may cause problems.
Read more in "about" button.

I will tell you how to auto mouse click in game "Sakura Clicker". (By sharing my AutoHotKey script with you) so you can AFK auto mouse click. Also useful for higher levels of game so that you won't destroy your mouse by mashing it.
While it is primary written for "Sakura Clicker" game this may also work for other games.
(see the end result below: auto clicking + "gold fountain" bonus, or however that was called).

steps:
1) Download autohotkey at http://ahkscript.org/ (I am using Version v1.1.22.03 Unicode 64-bit - but other (newer) versions should work too).
2) If during setup it will ask something like "do you want to associate AutoHotKey with .ahk extension?" - say yes. It will make launhing scripts more easily.
3) Go ahead and install it. Remember the path you have installed it to (most likely it was: "C:\Program Files\AutoHotkey" or "C:\Program Files (x86)\AutoHotkey")
4) When installation is done - open the "Notepad" and copy text (below) there.

go to a page:
https://pastebin.com/bu1b73nk
you can copy the entire script from there.

5) save it as: "sakura auto mouse clicker ( '[' and ']' ).ahk" without brackets. (what really important is: .ahk at the end - which is AutoHotKey's extension for scripts.)
6) now open the file that you have just saved. if the green "H" icon shows up in tray then it means the script is working. (see picture below).



now if you press "[" the auto clicking will start, and when you press "]" it will stop.
7) when you no longer need the auto click functionality stop the scipt with "]". and right mouse click "H" tray icon and select "exit".

Case of broken .ahk to AutoHotkey.exe extension association.
How to launch the script with this problem:

• If after step 6 a window poped-up asking "what program to open this with?" then navigate to path from step 3 - most likely C:\Program Files\AutoHotkey" or "C:\Program Files (x86)\AutoHotkey" and select "AutoHotkey.exe" there. press ok.
  
  try to open "sakura auto mouse clicker ( '[' and ']' ).ahk" now.
  still no luck? try to drag and drop "sakura auto mouse clicker ( '[' and ']' ).ahk" to AutoHotkey.exe. (see picture below)