The Reaction Time Game Game

The game is simple. Test the user's response time by asking them to enter the correct value that is displayed on the screen in the shortest time possible. Each round of the game will be as follows:


  Show Value ----> Get Response ----> Check Response ----> Report Response Time


Example

ROUND ONE
---------
COMPUTER : G
USER     : G
CORRECT INPUT, TIME = 0.26 SECONDS


Code


You may use any language or program.
Do not use third party libraries, except GUI libraries.
(as suggested by marinus)
You may choose between CLI and GUI.


Points


+12 for the shortest code
-2 for every byte after the 1024th byte
+8 for GUI
+8 for showing questions (eg: 4 + 2 = ?) (rather than static values shown in the example above. There must be at least 10 questions.)
+2 for random intervals between each round
+4 for reporting average response time (in a set of 10 rounds)
+4 for quickly vanishing questions/values
(questions/values stays on screen only for a short interval of time. The vanish time must be less than or equal to 1 seconds.)



  You must, in your answer, calculate the total points you have scored. eg (+12 (-2x3) +4 = 10)
JavaScript, ES6 352 340 335 bytes, Potential score : 2 + 8 + 12 + 4 + 4 + 8 = 38
&lt;script&gt;r=Math.random,s=setTimeout;T=N=0;a=_=&gt;(S=s(_=&gt;(C=eval(G.innerHTML=((k=~~(r()*5))+~~(r()*5))+'-'+k),t=new Date,R=s(_=&gt;C=G.innerHTML=a(clearTimeout(S)),r()*1e3)),r()*2e3+1e3),'');document.onkeyup=E=&gt;{clearTimeout(R);E.key==C&amp;&amp;++N&amp;&amp;(T+=(X=new Date-t))&amp;&amp;alert([X,N%10?'':T/10]);C=G.innerHTML=a(N%10||(T=0))};a()&lt;/script&gt;&lt;a id='G'/&gt;

or try this JSFiddle on latest Firefox.
Working:

Shows a random question in form of X-Y after a random interval of [2,4] seconds.
Waits for a keypress till a random time in an interval of [1,2] seconds, after which, clears the input and moves to step 1.
If correct number is pressed, alerts the time in milliseconds.
If this is the tenth (or rather every tenth) correct answer, show the average time in milliseconds for the last 10 correct answers after a comma.
Empties the input area, goes to Step 1 again.

Please comment if something is incorrect or if you have any doubts.