Is shift as a modifier key just unusable? I see many games and such use it like this so I'd think it'd be easy.

2. boolean wkey = false;
3. boolean skey = false;
4. boolean akey = false;
5. boolean dkey = false;
6. boolean shiftkey = false;
7. 
   
8. void setup() {
9.   size(100,100,P2D);
10.   noStroke();
11.   fill(0);
12. }
13. 
    
14. void draw() {
15.   background(255);
16.   textAlign(LEFT,TOP);
17.   text("W: " + wkey,0,0);
18.   text("S: " + skey,0,10);
19.   text("A: " + akey,0,20);
20.   text("D: " + dkey,0,30);
21.   text("Shift: " + shiftkey,0,50);
22. }
23. 
    
24. void keyPressed() {
25.   if(key == 'w') {
26.     wkey = true;
27.   }
28.   if(key == 's') {
29.     skey = true;
30.   }
31.   if(key == 'a') {
32.     akey = true;
33.   }
34.   if(key == 'd') {
35.     dkey = true;
36.   }
37.   if(key == CODED) {
38.     if(keyCode == SHIFT) {
39.       shiftkey = true;
40.     }
41.     
42.   }
43.   printKey("***** keyPressed", key,  keyCode);
44. }
45. 
    
46. void keyReleased() {
47.   if(key == 'w') {
48.     wkey = false;
49.   }
50.   if(key == 's') {
51.     skey = false;
52.   }
53.   if(key == 'a') {
54.     akey = false;
55.   }
56.   if(key == 'd') {
57.     dkey = false;
58.   }
59.   if(key == CODED) {
60.     if(keyCode == SHIFT) {
61.       shiftkey = false;
62.     }
63.   }
64.   printKey("^^^^^^^^^^^^^^^^^^^^^^^^^ keyReleased", key,   keyCode);
65. }
66. 
    
67. 
    
68. 
    
69. void printKey(String label, char myKey, int myKeyCode){
70.    String timeStamp = "time: " + millis() + ": "; // current time in milliseconds since sketch launch
71.    if ( myKey == CODED) {
72.        println(timeStamp + label + " --> CODED: " + myKeyCode);
73.    }
74.    else{
75.        println(timeStamp + label + " --> CHAR: '"  + myKey + "'");
76.    } 
77. }

@dimkir I ran into that while testing key functionality with a previous project and me and some others concluded that the reason some key combinations with more than two keys at once don't work is a hardware limitation of keyboards. Some gaming keyboards can apparently hold up to six or so keys at once, but normal keyboards usually only do more than 2 in key clusters. Though I'm not exactly sure how key clustering works on keyboards I guess it stops receiving more than 2 keys from different clusters.

more than two keys at once don't work is a hardware limitation

 

this is a great finding.  My best guess is that it depends on the wiring of the keyboards. I can press on my keyboard simultaniously "a" + "s" + "d" + SHIFT

but if I press "a" + "s" + "w" (and "w" is on the top row of the keyboard) then it doesn't get that key. Probably keys are wired on "rows" or smth. 

UPDATE:

I just googled 

https://www.google.ie/search?q=keyboard+wiring+simultaneous+key+presses

and it turns out that this phenomenon is called "Keyboard Ghosting"

http://www.microsoft.com/appliedsciences/antighostingexplained.mspx

Wow, live and learn every day! :)