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High Score Strategies

December 19, 1999
by Pat McClellan

Dear Multimedia Handyman,

I am going to program an online game by using Director 7. The problem that I'm facing right now is the database that will store the players' names and scores. I do not know what kind of database to be created. Can you give me an idea what kind of database to be used? If the database has been created, then how to send/add values/ characters that are typed in a field into the database when a button is clicked?

How to display the top 10 records from the database? Is it display it in a field too? If so, how to choose from the ten best players(with the highest scores) from the list of records in the database?

jeisum

Dear jeisum,

That's a lot of questions, and unfortunately, the answer is... it all depends. It depends on what you want to do and how you want to set it up. It depends on the server technology that you have available to you. And it depends on the game design and how many people will be playing the game at once. So, let's look at some options.

The first issue is whether the highscore system is networked, or rather just on the user's machine. We'll examine the networked option first. Let's say that your game is on a website in Malaysia. A guy named "John" in Chicago goes to your page where the Shockwave game downloads to John's computer and he plays your game. Remember that the game is actually running on John's computer, not from your server. Meanwhile, Francois in Paris also goes to your page, downloads and plays your game. At the end of John's game, his score is sent in a message back to your server. Your server sends back a list of the top 10 scores, so the Shockwave game still running on John's computer receives this list and displays the scores. It shows him that his score is the third highest, while Francois in Paris holds the top 2 spots.

This is an example where the highscore pits the player against everyone else in the world. Note that in this example, John and Francois are not actually playing the game against each other interactively. Rather, they each play a solitary game on their own computers and the scores are matched at the end. This is "asynchronous", meaning that John and Francois aren't necessarily playing at the same time. (Using the Multiuser Server, you could have many people playing the same networked game at the same time.)

To make such a highscore system, you'll need something on the server end to receive a message from the Shockwave game running on the user's computer. So what is that "something"? Typically, that would be referred to as a "cgi script". (CGI stands for "common gateway interface", but I really don't have any insight on what it means.) Think of a cgi as some kind of a processor on the server end. It receives the message from the internet, knows how to process it, perhaps saves the results in a text file or database, then returns a message to the sender. If this seems vague, it's simply because cgi can refer to a lot of different backend processors. For example, a cgi script can be a standalone computer program written in Perl (the most common language for CGI scripts, though there are other possible languages as well.) The webserver would need to be able to run Perl scripts.

Another likely alternative would be a database (Filemaker Pro, MS Access, or a generic datafile) which is accessed using Active Server Pages or Cold Fusion or any of the other web application development environments. Since each of these environments has its own protocol for interacting with the data, I can't be very specific about explaining how to send and receive the data. Basically, you'll use Director's postNetText command, calling a specific cgi URL on your server and supplying the score. (That URL is likely to end in .cgi, .asp, .jsp, .cfm, or something that indicates special processing.) It will take the score, insert it into it's appropriate spot in the highscore list and return the 10 top scores. (I strongly recommend you read Zac's article, Integrating with Cold Fusion. Even if you don't use Cold Fusion, the concepts are the same.)

Another possible "cgi backend" is a Director projector, using the multiuser server or multiuser xtra. This option will require the users to download the multiuser xtra, but that can be coded into the movie so that it happens automatically. If you go with the option, the Director projector will run on your server all the time. Everytime a user loads up your game, it will open a connection to the projector. The projector will keep track of the scores and take care of all the incoming and outgoing messages. If you choose this option, you'll need to master the multiuser server/xtra. We'll be featuring some articles on that in the near future. In the meantime, check Macromedia's site for documentation.

Whatever cgi backend you choose, you'll need to decide what you're really going to do with the data. Specifically, how many scores do you really want to store? If the Shockwave game only displays the top 10, is there any reason to save more than that? If not, it will be a very simple database -- storing ten records with fields for score, date and name. On the other hand, you might want to store data on all the games ever completed. In this case, the database would be much larger, and only a select portion of the data would be reported back the the user.

This whole approach is fairly elaborate and will require a significant learning curve. Let's examine another option which may suit your needs: a highscore system which is restricted to the user's machine. There is a developer named Bongwook Lee who has created some wonderful Shockwave games. He provides a fairly simple highscore approach which I have found quite satisfying as I've grown addicted to his Simulus game. The simple approach is that the highscores are the scores of users on a single computer. So as I play game after game, I'm competing against myself -- and my wife who also plays the game on my computer. Let's create this type of system.

Here's a demo where you can experiment with the features we'll be including.

A sample movie is available for download in Mac or PC format. This is a D7 movie.

Lists will adequately store the data we need to keep, and my first inclination was to go for a property list. But the design of this list is a little bit complicated. Let's think about what we want the list to be able to do. For any particular score, we'll want to store the points, the user's name, and the date. We'll need to be able to order the scores (with names and dates) from highest points to lowest points. So if we had a property list that was indexed by the points, we could just sort that list. The problem is that it's possible that you'll have more than one game with the same point total -- both of which need to be listed. As well, it's likely that the same person will play more than one game, and perhaps on the same date. In a property list, you can't have duplicate properties, so we can't index the property list by the values for points, names, or dates.

In Tab Julius' book "Lingo - An Advanced Guide", he suggests the use of parallel lists. So imagine that we have one list which stores all of the points, another list for the names, and a third list for the dates. So for any given game score, you'll store the point value in one list, the player's name in a second list, and the date in a third list. The trick is that these values are linked together by their position in their respective list. Take a look at these three lists:

pointList = [90,180,35,75,105,90,150,95,130,125]
nameList = ["Bob", "Carol","Carol", "Bob", "Alice", ¬
  "Bob", "Ted", "Ted", "Ted", "Alice"]
dateList = ["11/17/99", "11/17/99", "11/17/99", ¬
  "11/19/99", "11/18/99", "11/27/99", "11/23/99", ¬
  "11/19/99", "11/15/99", "11/27/99"]

For example, look at the fifth value in each list. They indicate that Alice played a game on 11/18/99 and scored 105 points. You can see that it's critical to maintain parallel order in the lists. So that means we cannot use the sort function. Doing so would royally screw up the system by breaking the linkage between points, players' names, and the dates. This is of importance when we need to list the scores in order of highest to lowest points. We'll get to that shortly.

We'll use setPref to store the lists in the user's prefs file. For ease in handling the three lists, I'm going to combine them into a single property list which I'll store in a global variable called gScores. Then, I'll save a string version of gScores using setPrefs.

gScores = [:]
addProp gScores, #points, pointList
addProp gScores, #names, nameList
addProp gScores, #dates, dateList
setPref("myScores", string(gScores))

So now, gScores is a property list containing all three lists, and it looks like this:

put gScores
-- [#points: [90, 180, 35, 75, 105, 90, 150, 95, 130, 125], ¬
  #names: ["Bob", "Carol", "Carol", "Bob", "Alice", "Bob", ¬
  "Ted", "Ted", "Ted", "Alice"], #dates: ["11/17/99", ¬
  "11/17/99", "11/17/99", "11/19/99", "11/18/99", ¬
  "11/27/99", "11/23/99", "11/19/99", "11/15/99", ¬
  "11/27/99"]]

When the game initially loads (on startMovie), I'll use getPref to retrieve the value for gScores from the user's prefs file. That file won't exist the very first time the user plays, so you have to allow for that possibility in the script.

on startMovie
  global gScores
  
  scoreString = getPref("myScores")
  if voidP(scoreString) then 
    -- no scores saved yet
    clearScores
  else
    -- convert prefs string to list
    gScores = value(scoreString)
  end if
  
end startMovie
on clearScores
  global gScores
  
  pointList = [0,0,0,0,0,0,0,0,0,0]
  nameList = ["", "", "", "", "", "", "", "", "", ""]
  dateList = ["", "", "", "", "", "", "", "", "", ""]
  gScores = [:]
  addProp gScores, #points, pointList
  addProp gScores, #names, nameList
  addProp gScores, #dates, dateList  
  setPref("myScores", string(gScores))
  
end clearScores

This initializes the global variable gScores, using the value stored in the prefs file -- if there was already a value there. If the game has never been played on that computer, then there won't be a value in the prefs file (void), so the clearScores handler sets the initial values for zero and writes that to the prefs file.

We'll need a behavior to apply to the text sprite so that the values in gScores can be displayed on the stage. I set up a text member, picking the color and font and setting the tabs for the display I want. Then, apply this behavior:

global gScores
on beginSprite me
        displayScores me
end beginSprite
on displayScores me
  -- separate the 3 lists from gScores
  pointList = gScores.points
  nameList = gScores.names
  dateList = gScores.dates
  
  -- create rankOrder list
  rankOrder = []
  pointListCopy = duplicate(pointList)
  repeat with i = 1 to 10
    topPosition = getPos(pointListCopy, ¬
      max(pointListCopy))
    add rankOrder, topPosition
    pointListCopy[topPosition] = 0
  end repeat
  
  -- build the text string
  displayText = ""
  rank = 0
  
  repeat with whichPos in rankOrder
    rank = rank + 1
    thisPoints = pointList[whichPos]
    thisName = nameList[whichPos]
    thisDate = dateList[whichPos]
    thisLine = TAB & rank & ":" & TAB & thisPoints & ¬
      TAB & thisName & TAB & thisDate 
    displayText = displayText & thisLine & RETURN
  end repeat
  
  sprite(me.spriteNum).member.text = displayText
  
end displayScores

The displayScores handler is where we have to deal with pulling corresponding values from each of the three lists. I start the handler by separating out the three lists from the whole gScores list. Now I explained earlier that we can't sort the scores list without screwing up our parallel lists. So we need another way to get the order of the lists from highscore to low. Take a look at this example:

put gScores.points
-- [90, 180, 35, 75, 105, 90, 150, 95, 130, 125]

This is the pointList from gScores. You can see that they aren't in sorted order, but remember that we don't want to change the order because it corresponds to the other lists. So let's create another list called rankOrder. The rankOrder list will tell us the position in the pointList of the highest to lowest scores. So for the example above...

rankOrder = [2, 7, 9, 10, 5, 8, 1, 6, 4, 3]

You see that the first value in rankOrder is 2 because the highest score in our pointList above is the second value -- which happens to be 180 (irrelevant). The next highest score is the 7th value, followed by the 9th, 10th, 5th, 8th, 1st, 6th, 4th... and the 3rd value in the pointList is the lowest. Note that since the 1st and 6th scores are the same, it really doesn't matter which of the two goes first.

So that's the concept. Setting rankOrder from the pointList is a little tricky, as you can see in the code of the displayScores handler. But once we have the rankOrder list, it's a breeze to parse the corresponding values from our three data lists. By the way, my variable "rank" has to do with the 1 to 10 that appears on the left side of the stage display. Don't confuse it with rankOrder.

All that's left is to enter a player's new score into the list. This won't happen every game, only when the currentScore is greater than the lowest of the 10 high scores. When that happens, that lowest score will get replaced by the new score -- along with the player's name and the current date. Note that the new score probably won't be the lowest, so when a new score goes in, the rankOrder will change.

Here's the movie script needed to set a score. When you call this handler (when the game is over) you'll need to supply the value for the currentScore. This handler starts by checking to see if the currentScore is greater than or equal to the minimum value in the pointList. If so, the variable "bumpedPos" is set to the position (not value) of the lowest score in the pointsList. Then the new data is inserted into each of the three lists using the bumpedPos variable to keep them linked to each other.

on setScore currentScore
  global gScores
  
  pointList = gScores.points
  lowestHighScore = min(pointList)
  
  if currentScore >= lowestHighScore then
    bumpedPos = getPos(pointList, min(pointList))
    gScores.points[bumpedPos] = currentScore
    gScores.names[bumpedPos] = member("name").text
    gScores.dates[bumpedPos] = the short date
    setPref("myScores", string(gScores))
  end if
  
end setScore

Now that you know how it all works, play with the demo movie above. Enter a score which is lower than the lowest value there. Notice that the value is not added to the list. Add a score that is equal to one of the other values. If it's the lowest value, then the newer score replaces the older one.

This system is not the answer for a networked online game, but it's a pretty good solution for individual competition or a kiosk game situation. Good luck with your program!

Patrick McClellan is Director Online's co-founder. Pat is Vice President, Managing Director for Jack Morton Worldwide, a global experiential marketing company. He is responsible for the San Francisco office, which helps major technology clients to develop marketing communications programs to reach enterprise and consumer audiences.

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