//Declare and initialize global variables
  var expression = "";   //The equation to be solved
  var A = 0;             //Random number for the equation
  var B = 0;             //Random number for the equation
  var answer;            //Hold the answer that is entered
  var rightAns;          //Hold correct answer
  var counter = 0;       //Count the number of equations generated
  var correct = 0;       //Count the number of correct answers
  var incorrect = 0;     //Count the number of incorrect answers
  var L = 0;             //User request for lowest random number
  var H = 12;            //User request for highest random number
  var t = 61;            //Set starting value for timer countdown -- LINE 20
  var ticker;            //Variable for setTimeout
     
//Reinitialize global variables
function initialize() {
  expression = "";   //The equation to be solved
  A = 0;             //Random number for the equation
  B = 0;             //Random number for the equation
  counter = 0;       //Count the number of equations generated
  correct = 0;       //Count the number of correct answers
  incorrect = 0;     //Count the number of incorrect answers
  t = 61;            //Set starting value for timer countdown
  document.mmForm.timeClock.value = 60;
  document.mmForm.question.value = expression;
  document.mmForm.answer.value = "";
  document.mmForm.correct.value = correct;
  document.mmForm.incorrect.value = incorrect;
}

//Create fuction to stop active game without re-initializing everything
function stopPlay() {                                   //LINE 40
  expression = "";   //The equation to be solved
  A = 0;             //Random number for the equation
  B = 0;             //Random number for the equation
  document.mmForm.question.value = expression;
  document.mmForm.answer.value = "";
}

function countDown() {
  t--;
  if (t > 0) {
    ticker = setTimeout('countDown()', 1000);
    document.mmForm.timeClock.value = t;
  } else {
    //Time is up, so stop and show final score
    clearTimeout(ticker);
    document.mmForm.timeClock.value = t;
    stopPlay();
    showResult();
  }                                                               
}                                                    //LINE 60

//When time runs out, display the results
function showResult() {
    var z = eval(correct + incorrect);
    alert("Time's up! Out of " + z + " tries, you got " + correct + " right and " + incorrect + " wrong.");
}

//Generate two random numbers between L and H
function genNumbers() {
  H = eval(document.mmForm.hiNum.options[document.mmForm.hiNum.options.selectedIndex].value);
  L = eval(document.mmForm.loNum.options[document.mmForm.loNum.options.selectedIndex].value);  
  //Make sure H >= L
  if (L > H) {
    var K = L;
    L = H;
    H = K;
    //Change hiNum and loNum readouts if needed
    document.mmForm.hiNum.options.selectedIndex = H-1;
    document.mmForm.loNum.options.selectedIndex = L;
  }                                                  //LINE 80
  
  A = Math.floor((Math.random() * (H - L + 1)) + L);
  B = Math.floor((Math.random() * (H - L + 1)) + L);
  //Make sure A and B do not both equal zero
  if ((A == 0) && (B == 0)) {
    while (A == 0) {
      A = Math.floor((Math.random() * (H - L + 1)) + L);
    }
  }
  getOperation();
}

//Match the two random numbers to the right operation
function getOperation() {
  if (document.mmForm.operation.options.selectedIndex == 0) {
    add(A, B);
  }
  if (document.mmForm.operation.options.selectedIndex == 1) {
    subtract(A, B);
  }                                                   //LINE 100
  if (document.mmForm.operation.options.selectedIndex == 2) {
    multiply(A, B);
  }
  if (document.mmForm.operation.options.selectedIndex == 3) {
    divide(A, B);
  }
  //If random operation is selected, generate a random number between 0 and 3
  if (document.mmForm.operation.options.selectedIndex == 4) {
    var K = Math.floor(4 * Math.random());
    if (K == 0) {
      add(A, B);
    }
    if (K == 1) {
      subtract(A, B);
    }
    if (K == 2) {
      multiply(A, B);
    }                                              
    if (K == 3) {
      divide(A, B);                                  //LINE 120
    }
  }
}

//Generate addition expression
function add(x, y) {
  expression = x + " + " + y;
  document.mmForm.question.value = expression;
  rightAns = eval(expression);
  document.mmForm.answer.value = "";
  document.mmForm.answer.focus();
}

//Generate subtraction expression
function subtract(x, y) {
  if (x < y) {
    var z = x;
    x = y;
    y = z;
  }                                             //LINE 140
  expression = x + " - " + y;
  document.mmForm.question.value = expression;
  rightAns = eval(expression);
  document.mmForm.answer.value = "";
  document.mmForm.answer.focus();
}

//Generate multiplication expression
function multiply(x, y) {
  expression = x + " * " + y;
  document.mmForm.question.value = x + " x " + y;
  rightAns = eval(expression);
  document.mmForm.answer.value = "";
  document.mmForm.answer.focus();
}

//Generate division expression
function divide(x, y) {
  //Prevent division by zero
  if (eval(y) == 0) {                          //LINE 160
    var temp = y;
    y = x;
    x = temp;
  }
  var z = eval(x * y);
  expression = z + "/" + y;
  document.mmForm.question.value = z + " / " + y;
  rightAns = eval(expression);
  document.mmForm.answer.value = "";
  document.mmForm.answer.focus();
}

//Trim spaces and zeros from front of answer and spaces off the back
function trim(inputStr) {
  //Make sure the zero is not a legitimate answer
  if (inputStr != "0") {
    //Then trim zeros and spaces off the front 
    while ((inputStr != "0") && ((inputStr.charAt(0) == " ") || (inputStr.charAt(0) == "0"))) {
      inputStr = inputStr.substring(1, inputStr.length);
      document.mmForm.answer.value = inputStr;             //LINE 180
    }
    //Then trim spaces off the back
    while (inputStr.charAt(inputStr.length - 1) == " ") {
      inputStr = inputStr.substring(0, inputStr.length-1);
      document.mmForm.answer.value = inputStr;
    }  
  }
}

//Check the answer to be sure it's all numbers
function isNum(inputStr) {
  for (var i = 0; i < inputStr.length; i++) {
    var aChar = inputStr.charAt(i);
    if ((aChar < "0") || (aChar > "9")) {
      alert("Please enter only numbers.");
	return false;
      break;
    }
  }
  return true                                         //LINE 200
}

//Handle routing logistics of checking the answer to be sure it's all numbers
function checkIt(inputStr) {
  if (isNum(inputStr)) {
    //inputStr is a number
     checkAnswer(inputStr);
  } else {
    document.mmForm.answer.focus();
    document.mmForm.answer.select();
  }
}

//Check the answer to see if it's right
function checkAnswer(answer) {
  //Make sure an expression has been generated and the question answered
  if ((document.mmForm.question.value != "") && (document.mmForm.answer.value != "")) {
    //When it's right, score it
    if(parseInt(answer) == rightAns) {
      correct++;                                       //LINE 220
      counter++;
      document.mmForm.correct.value = correct;
      genNumbers();     //If not, generate a new expression
    } else {   
   //If it's wrong, tell the user
      incorrect++;
      counter++;
      document.mmForm.incorrect.value = incorrect;
      alert("Sorry: " + document.mmForm.question.value + " = " + rightAns);
      genNumbers();     //If not, generate a new expression
    }
  } else {
    if (document.mmForm.question.value == "") {
      alert("Click 'Go' to see your first problem.");
      initialize();
    } else {
    alert("Oops! You forgot to enter an answer.");
    document.mmForm.answer.focus();
    }
  }                                                    //LINE 240
}

// JavaScript Document