fix some file extensions

Task/Rock-paper-scissors/0DESCRIPTION

@@ -9,3 +9,5 @@ Rock Paper Scissors is a two player game. Each player chooses one of rock, paper
 If both players choose the same thing, there is no winner for that round.
 
 For this task, the computer will be one of the players. The operator will select Rock, Paper or Scissors and the computer will keep a record of the choice frequency, and use that information to make a [[Probabilistic choice|weighted random choice]] in an attempt to defeat its opponent.
+
+'''Extra credit:''' easy support for [[wp:Rock-paper-scissors#Additional_weapons|additional weapons]].

Task/Rock-paper-scissors/REXX/rock-paper-scissors.rexx

@@ -0,0 +1,36 @@
+/*REXX pgm plays rock-paper-scissors with a CBLF (carbon-based life form*/
+!='────────';   er='***error!***'; @.=0         /*some constants for pgm*/
+z=! 'Please enter one of:     Rock  Paper  Scissors      (or Quit)'
+$.p='paper';    $.s='scissors';    $.r='rock'     /*computer's choices. */
+b.p=' covers '; b.s=' cuts ';      b.r=' breaks ' /*how the choice wins.*/
+
+  do forever;   say;    say z;    say  /*prompt the CBLF & get response.*/
+  c=word('rock paper scissors',random(1,3))    /*the computer's 1st pick*/
+  m=max(@.r,@.p,@.s);   f='paper'      /*prepare to examine the history.*/
+  if @.p==m  then f='scissors'         /*emulate JC's The Amazing Karnac*/
+  if @.s==m  then f='rock'             /*   "     "    "     "       "  */
+  if m\==0   then c=f                  /*choose based on CBLF's history.*/
+  c1=left(c,1);   upper c1             /*C1  is used for fast comparing.*/
+  parse pull u;   a=strip(u);          /*get the CBLF's choice (answer).*/
+  upper a;        a1=left(a,1)         /*uppercase answer, get 1st char.*/
+  ok=0                                 /*indicate answer isn't OK so far*/
+       select                          /*process the CBLF's choice.     */
+       when words(u)==0           then say  er  'nothing entered'
+       when words(u)>1            then say  er  'too many choices: '  u
+       when abbrev('QUIT',a)      then do;  say ! 'quitting.';  exit;  end
+       when abbrev('ROCK',a)  |,
+            abbrev('PAPER',a) |,
+            abbrev('SCISSORS',a)  then ok=1    /*a valid answer by CBLF.*/
+       otherwise                  say er  'you entered a bad choice:'  u
+       end   /*select*/
+
+  if \ok          then iterate         /*answer ¬ OK?  Then get another.*/
+  @.a1 = @.a1+1                        /*keep track of CBLF's answers.  */
+  say ! 'computer chose: '  c
+  if a1==c1              then do; say ! 'draw.';  iterate;  end
+  if a1=='R' & c1=='S' |,
+     a1=='S' & c1=='P' |,
+     a1=='P' & c1=='R'  then say ! 'you win! '            ! $.a1 b.a1 $.c1
+                        else say ! 'the computer wins. '  ! $.c1 b.c1 $.a1
+  end   /*forever*/
+                                       /*stick a fork in it, we're done.*/