The Game It'll consume all of your free time – seriously

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Features of Online Sudoku More advanced features than you can shake a stick at

Online Sudoku is easier to use yet more powerful than 95% of computer-based sudoku games out there. It's surprisingly full-featured. The following is a list of just a handful of the cool features it sports:

• Beautiful, Easy-to-Use Interface We promise, you've never seen an interface this simple and easy-to-use for a computer-based sudoku game—much less an online game.
• Keyboard Shortcuts Never before has playing sudoku on a computer been so easy! Dozens of powerful keyboard shortcuts make it almost as intuitive as playing with pen and paper—an in a web-browser, no less.
• Powerful Marks System A problem with most computer sudoku games is that their marks are too darned hard to use easily. Online Sudoku makes it easier than you ever thought possible.
• Hundreds of Puzzles With hundreds of puzzles to play in four difficulty levels, you'll never run out.
• Input Custom Puzzles Want to play a real-world puzzle in the application? No problem—with the built in custom mode, it couldn't be easier to enter a puzzle you've seen elsewhere and be playing it within seconds!
• Save Your Progress Automatically save your progress across multiple sessions. A sophisticated auto-save ensures that you'll never lose your progress again.
• Play on a Plane or in a Car Because this game is web-based, you'd think you wouldn't be able to take it with you on a long trip. Wrong. Online Sudoku features a powerful offline mode that can queue up to 20 puzzles for playing when you're in the air or on the road.
• Play it Anywhere Because Online Sudoku is web-based, you can fire it up on any computer that has access to the internet.
• Share Puzzles With Friends You can easily generate links for your friends to your puzzle with all of your current progress, or to the a blank version of the puzzle you're working on. See who can solve the puzzle the fastest!
• Hall of Fame Registered users have the chance of showing up on the top scores list, letting everyone else know just how awesome they are at sudoku.
• Undo/Redo Multiple Levels Hit the 'u' key to undo, the 'r' key to redo. Online Sudoku lets you undo/redo to your heart's content.
• Sophisticated Hint Feature Never again will you get stuck on a hard puzzle. Online Sudoku's sophisticated hint feature can help out with almost any puzzle and—what's better—it'll let you know the logic behind the hint it's giving you.
• Automatic Time Penalties In order to make the Hall of Fame times fair, if you use a time-saving feature your solve-time will be adjusted accordingly.
• It's FREE Most computer-based sudoku games worth their salt want you to pony up money to download and play. Online Sudoku is 100% free—and has more features than a lot of the other computer-based sudoku games combined!

How to Use Online Sudoku It's really not that hard

What does this online version of sudoku have to do with other versions? It's an online version of sudoku. What makes this one different from all the others? It kicks their butt, that's what.

The Basics

Click a space to select it. Hit a number key to place it in that space, or zero to clear the space. Or, if keyboard shortcuts aren't your thing, use the Numbers panel on the right of the gameboard (click it once to expand it) for handy-dandy buttons that do the same thing.

Marks

What would an online sudoku game be without marks? You can use the marks panel on the left of the board to toggle a mark for the selected space, or use Ctrl + Number to do the same thing (those of you on Safari, use Control + Number). Remember that marks are only visible if the space is empty—placing a number in a space won't get rid of the marks for that space, but rather just hide them.

Picking a New Puzzle

Although it might surprise you, you can play puzzles other than the default one. Use the difficulty selector drop-down box to pick a difficulty, and hit the "New" button to load up a new puzzle. The game retrieves a fresh puzzle off the server every time you load a new puzzle; you could play thousands of different puzzles without ever refreshing the page! Even better, a large handful of puzzles are kept on hand all the time just in case you lose connection to the internet, which is perfect if you want to play on the plane!

Saving and Loading

Say you're half-way through solving a difficult puzzle when your battery's about to run out. No problem, just hit the "Save" button—next time you visit the game, your puzzle will be ready and waiting for you to bring it back to life by hitting the "Load" button. Even better, the game will automatically save its progress when you leave the page, so you'll never have to worry about losing any of your brilliant deductive work! (Sorry Opera users, auto-save won't work for you.)

Other Things

Hit the "Reset" button to clear out the puzzle and reset the timer, just like you loaded up a new puzzle. Although we know you'd never do such a thing, the pause button comes in handy if you want to quickly take a break and jot down what the professor's saying while you're playing.

Stuck? Online Sudoku has a built-in solver that's suprisingly good. Just hit the "Hint" button or tap the 'H' key, and the game will tell you which space to fill in next, and how it came to arrive at that conclusion.

Make a mistake? Don't worry; you can undo and redo as many times as you like. Just hit the "U" key to undo, or the "R" key to redo.

Timer making you nervous? Just hit the timer's text once to disable it from updating while you're playing. When you finish the game, it'll still let you know how long you took.

Custom Puzzles

You aren't just limited to the puzzles that we give you! Select "Custom" in the difficulty drop-down selector and define your own puzzle—or a puzzle you've got from somewhere else. Once you're done inputting the puzzle, hit the "Start" button to begin actually playing it. If you want to make changes to the puzzle, hit the "Edit" button—but beware, entering design mode will reset the current puzzle's progress.

Keyboard Shortcuts

Are you a sudoku fiend? Want to be even faster? This sudoku game has more keyboard shortcuts than you can shake a stick at. Expand the "Shortcuts" panel at the top of the game to see a helpful list of them. Here are a few of the highlights:

• Move Spaces Use the arrow keys to move the selected space one unit in that direction. Use Ctrl + Arrow to skip over filled spaces.
• Number Key Use the number keys to place a number in a space. Hold down Ctrl when pressing to toggle that mark in the space.
• Pause Hit 'p' to pause the timer.
• Save Hit 's' to quickly save your progress. Make it a habit, and you'll never lose your progress again.
• And more... Check out the shortcuts tab above the game board for a list of all shortcuts!

Cheating

Never before has cheating been so easy in sudoku. By default, the game will let you know if you've put in an invalid number in a space—that is, one that conflicts with another space in its row, column, or box. In addition, spaces with any invalid marks will have their marks show up in red. Finally, if you want to really cheat, you can make it so that the space will be highlighted if the number you type in is incorrect, period, not just invalid. This feature only works with non-custom puzzles. Don't like cheating? That's cool—all of these options can be turned on or off by expanding the "Options" panel below the game.

Marks can help out a bunch, too, especially when they're semi-automatic. Although you'd never know it without using keyboard shortcuts, this sudoku game has some seriously powerful features to help you mark like there's no tomorrow. Hit the plus key to fill a space with all of its valid marks, or the minus key to remove any marks that are invalid. That's cool, but what's even cooler is that hitting Ctrl + Plus and Ctrl + Minus will work on all of the spaces at once.

Just remember: if you rely on these features too much, you really shouldn't say "I solved the puzzle" without sheepishly adding "...with a lot of help from the game." Also, cheating isn't all great: it comes with penalties.

Penalties

It used to be that if you "cheated," the only person you were affecting was yourself—kind of like cheating at solitaire. With the Hall of Fame, however, suddenly if you cheat you're suddenly affecting others by artificially climbing the Hall of Fame. That's not fair!

That's why Online Sudoku has a robust penalty system. If you "cheat," you'll be docked a corresponding number of seconds. This makes it so that you can't get ridiculously low solve times. Every time you "cheat," you'll be assessed a penalty, which will be automatically added to your solve time. Times in the Hall of Fame that had penalties applied will show up with asterisks after them so others will know you're a cheater. The table below shows how much each kind of "cheating" costs.

Most of these are pretty straight forward: you ask for a hint, you get 60 seconds added to your time. Others aren't as clear: how can you get docked .5 seconds for invalid mark highlighting? For any of the highlight cheats, the penalty will be assessed every time the given item is highlighted. That is, you could have the "Show Invalid" option checked and never be assessed any penalties because you never filled in a space invalidly. Every individual time you put in an invalid number (and you have "Show Invalid" checked), however, you'll be docked a small amount.

As penalties are assessed, the timer will fade out and fade in with the adjusted time. Cool, huh? You can also get a status update if you lose track while you're solving. Just tap the 'N' key and a helpful window will pop up showing you which penalties have already been assessed so far for this puzzle and how much they're costing you.

Did you just solve a whole puzzle by yourself only to find that you were assessed some penalties anyway? The reason is because by default the options are set to have invalid spaces and marks highlighted, which is a form of cheating. The simple answer is just to uncheck those two options. Expand the control panel by hitting the "Options" button, then uncheck all of the check boxes. Problem solved!

Incorrect? Invalid? What's the Difference?

I know, the distinction can be somewhat subtle, but I promise, it makes sense. Think of it this way: something that is incorrect is absolutely wrong. Something that is invalid is relatively wrong. There's often a lot of overlap, which leads to some confusion. Each and every sudoku puzzle in Online Sudoku (with the exception of perhaps some custom puzzles you devise) has exactly one solution. If you put the wrong number in a given space, the game knows that it is absolutely wrong. This is an incorrect space. But when you're playing a game, you can't just magically figure out what each space should be from the start; you need to use surrounding spaces as clues and gradually build up information. It's possible to put in a number that contradicts what you know right now. This doesn't mean that it's absolutely wrong—maybe the spaces you already filled in are wrong—it just means that the space you just filled in is inconsistent with what you've filled in so far. This is an invalid space. You, personally, should be able to tell relatively easily if a space you fill in is invalid—the highlighting just makes it easier to notice. On the other hand, no human could ever know when a space is flat out incorrect just by glancing at the board, so having the game highlight incorrect spaces is practically cheating.

Does this still not make sense? Just leave the options how they are by default and forget that there even is a difference!

How To Play Sudoku The definitive guide for the ten people who still don't know how to play

It never fails – once you think that every single person in the world has played sudoku or at least knows the rules, you find out that someone has been living in a cave for the past ten years and has no clue what to do. That's fine, because sudoku has seriously the easiest rules ever. The goal is to put a number in every space so that one of each number is in each row, column, and 3x3 box. That's it. Seriously.

Right now you might be thinking, "that's sounds like the easiest and therefore dumbest game that I've ever heard of," or maybe you're thinking, "wow, that sounds ridiculously hard – I haven't done math since middle school!" Sudoku isn't that easy, and it isn't that hard. In fact, it doesn't have anything at all to do with math. You could use letters just as easily.

Sudoku is really all about logic. If you're just starting out, switch the difficulty selector to "Beginner." These puzzles are much easier than other puzzles, even if they don't look any different. Online Sudoku is really great for learning – if the number turns red when you put it in, that means you broke one of the rules, and you should look for the other red numbers to see which ones conflict with what you just put in.

If you want to learn by cheating, hit Ctrl + Plus key to fill every space with all valid marks – that is, every number that is valid in that space given its neighbors. Then, just look for the spaces that only have a single number in them, and place that number. Every so often, hit Ctrl + Minus key to clear out all of the newly-invalid marks. Keep in mind that like 98% of sudoku players would consider this flat-out cheating, so just rely on this technique while you get the hang of what sudoku is all about, but move on to real sudoku as soon as you feel comfortable.

Keep in mind that marks are 100% just for you. All that matters for winning is that all of the numbers are in the right place when you're done. More experienced players won't use marks at all for easy puzzles.

As you play more and more, you'll learn little logic rules that will help you get faster and faster. You'll learn the value of looking at a single box and just counting until you figure out what numbers are valid. It's fun, we swear. Just give it a try.

Change Log

February 2nd, 2008 Version 1.2 released

I know that it feels like nothing has happened to Online Sudoku since July. But that's not actually the case. In reality, a lot of work has been done to clean up the code and fix bugs while having the user experience stay the same. Now, it's easier than ever for me to deploy new features fast.

Today a whole bunch of new features and improvements are launching. The biggest and most obvious is the brand new penalty feature.

I've received a lot of comments from users complaining that other people in the Hall of Fame have clearly used a lot of the helpful features of Online Sudoku to get their solve times absurdly low. Of course, that's not fair. But neither would be removing those helpful features that you've come to love. The answer is penalties. When you perform time-saving tasks while solving the puzzle, a small penalty will be assessed and added to your solve time automatically. Most things add a second or less, but some, like the hint feature, will add a whole 60 seconds to your time.

When you're assessed a penalty as you're working on the puzzle, the timer text will fade out and quickly fade back in with the adjusted time. When you solve the puzzle, a little asterisk will show up next to your time if any penalties were assessed. If you click the 'More information...' link, a helpful table will expand showing you exactly which penalties were assessed how many times, and how much they cost you. The Hall of Fame will also show an asterisk next to any time where penalties were assessed.

But what if you want to do a quick spot check while you're working on the puzzle, to see how many penalties you've racked up so far? No problem; there's a new shortcut for that. Just tap the 'N' key and a helpful dialog box will pop up with a break-down of your current penalties.

Be aware that you'll rack up penalties every time that marks are highlighted (showing them to be invalid) or a number is highlighted (showing it to be invalid). Those two features are turned on by default, so if you want to try to solve a puzzle with no penalties whatsoever, you'll want to turn off those options.

Special thanks go out to Rob, the user who first suggested this feature. I really think that you'll love it. If not, let me know!

But of course, the penalty feature isn't all that I've been up to. Here's a partial list of important bug fixes and features:

• Faster puzzle loading I've made quite a few changes to how puzzles are fetched from the server. This means that you'll always get 20 puzzles by default whenever you fire up the application; there's no need to change the number of loaded puzzles in the option menu. Also, puzzles are buffered for every difficulty, meaning that switching difficulties is now faster than ever!
• Option to disable interface hints A few users have written to complain about the interface hints that pop up every so often below the game. Replacing the old option to change how many puzzles are pre-loaded is a new option to change how often those hints are shown—or even to turn them off entirely. Hit the "Options" button to expand the control panel, then use the select box to change the frequency of the interface hints.
• Vastly improved apperance on Internet Explorer I've taken a lot of time to get the interface to look (almost) as nice on Internet Explorer as it does on the rest of the browsers. There are still a few lingering display bugs (debugging CSS for Internet Explorer is one of the most frustrating tasks on the planet) but the look is vastly improved.
• Interface hints now display correctly It used to be that the statusbar—the area where the interface hints appear periodically—was not always sized correctly to contain its content. That problem has been fixed.
• The pointer for hints is positioned intelligenty It used be that in some cases, when you asked for a hint in the gadget version of the application, the hint box would run off the edge of the page. Now, the hint can point both left, right, above, and below, so it can be positioned to not run off the page.

July 25th, 2007 Hundreds of New Puzzles

It's been a long time since the last update, but rest assured that work continues on Online Sudoku! A few bug fixes and behind-the-scenes code refactoring have been going on recently. Notably, the bug where in Internet Explorer logged in users weren't having their options rememebered is now fixed.

More excitingly, the database has now been stocked to the brim with engaging new puzzles for every difficulty. These puzzles are generated by the excellent open source QQWing sudoku puzzle generator. Expect regular updates with hundreds of new puzzles.

Keep on checking back, because we've got a lot of cool features in the pipeline. As always, we love to hear your feedback and suggestions.

February 23rd, 2007 Undo/Redo Functionality Added

It used to be that if you made a mistake you had to either start over or tediously try to retrace your steps. No longer! Online Sudoku now sports a nifty undo/redo feature. Just hit the 'u' key to undo, or the 'r' key to redo. You can back all the way up to when you started the puzzle, if you want. Just remember that resetting the puzzle will lose all of your undo progress (it'll warn you before resetting), and undo histories are not saved when you save or share a game.

January 31st, 2007 Added Advanced Branch Mode Solver Tool

Sudoku can be hard. Every so often you come across puzzles that can't be solved by logic alone—at some point you have to make a guess. Some people don't consider these puzzles true sudoku puzzles. Others just think they're annoying. One thing's for sure: these special puzzles are hard. Continue reading for an explanation of the branching technique and how the new branch mode helps you out.

Say that you've gotten to a point in a hard puzzle where you are just sure that no more spaces can be filled in with logic alone. What do you do? You branch. Basically, you pick a space that has only two possibilites, and you pick one at random. There are two possible outcomes: either you picked the right one and you can follow this path to completion, or you picked the wrong one and you'll come to a contradiction. If you picked the right path the first time, you're done. If you picked the wrong one, you've got to backtrack to the point where you made the unfortunate guess. This is called branching, and it is, quite frankly, a pain in the butt. Traditionally, players will make a small mark in any space they modify after branching—that way, if they picked the wrong path, all they have to do is erase the spaces with the mark in them and not (gasp!) the whole puzzle.

The new branch mode feature automates this process for you. The branch button is for advanced solvers only, and so it is hidden. You've got to slide out the options panel to see it. Alternately, hitting the 'b' key on your keyboard is just the same as hitting the button once. Turning on branch mode means that all of the changes you make from that point on will be tracked, and a red dot will show up in the bottom right corner of any changed space. When you turn off branch mode, the game will undo all the progress you made while branch mode was on. (Don't worry, it will warn you that you'll lose your progress and give you a chance to cancel before going through with it.)

Also, the hint giver will try to help you spot contradictions. If you're in branch mode and you request a hint when there is a space that is a contradiction, the hint will draw your attention to it and suggest you go back to the branch point.

Branch mode integrates well with all of the other features. If you save a game or send it while in branch mode, it'll remember which spaces have changed since the branch, and what their original values were. Basically, the branch mode makes a really tedious task just a bit more bareable. Happy solving!

Reminder Branching is an advanced technique. If you think you need to branch on any puzzle that isn't of "Advanced" difficulty, you should look closer—you're probably missing something.

January 28th, 2007 Added Exclusive Triples Hint Technique, Forgotten Password Feature

The hint algorithm now has a new technique added. It can now apply the exclusive triples technique when all else fails. This technique isn't used very often, but it should make the hint giver able to help out more frequently.

Also, now if you forget your password, you're not out of luck. Just go to the login screen and hit Forgot Password. An e-mail will be sent to you that will have a link that allows you to log in once without your password. Once logged in, you can change your password to something you'll remember.

January 22nd, 2007 UI Changes, Hint Button Added

You'll notice that the list of buttons now includes a button to generate a hint, as well as the button to share the puzzle (that button has been around for awhile, but it used to be hidden in the extra options slide-out). This makes these features more usable and, of course, discoverable. Also in this update are a few minor bug updates.

January 15th, 2007 The Hint System Grew a Brain. Seriously.

History books in the future will mark January 15th, 2007 as the day that Online Sudoku gained consciousness and began its slow but steady domination of humanity. Well, not really. But Online Sudoku is now so unbelievably good at giving hints that you'll swear it's got a brain hidden somewhere. Hints still work the same way as they did a few days ago, but now it's much smarter. If you get stuck, chances are it can figure out which number goes in some space or another. Not only that, but it'll be able to tell you how it came to that conclusion.

Have advanced puzzles simply been too hard for you to attempt before? Well now they aren't. If you get stuck, just hit that handy 'h' key and you'll be on your way in no time. Also, expect big improvements to the algorithm in the coming days. Yep, you heard right, it's going to get smarter. Who knows, soon Online Sudoku might be able to solve any puzzle you throw at it—all by itself.

In Other News... The Safari shortcut for removing all invalid marks is now fixed. Also, some of the serious display issues that cropped up in the new version of Opera are now fixed. It turns out the new version of Opera had changed one thing to improve "performance" that had the unfortunate side effect of making some text not show up. Opera users still may have a slightly sub-optimal experience, due to a few other quirks in Opera's DOM implementation.

January 13th, 2007 Added Hint Feature, Handful of Bug Fixes

Every so often, you simply get stuck and can't figure out the next move, no matter how hard you try. Today there's a new feature to help in these situations. Just hit the 'h' key to show a puzzle hint. These hints will point to a space, select it, and tell you what specific number, given what you've filled in already, the space must be filled by. The algorithm that creates the hints is pretty simple right now—the problem of creating good hints is actually computationally very intensive—but expect a constantly improving level of sophistication in the feature.

Also in this update are a whole bunch of bug fixes, many of them to problems that no sane person would have ever run across. Online Sudoku has a whole bunch of cool features, like user log-in, design mode, custom mode, offline mode, and user registration. When these different modes happen at the same time, sometimes some unpredictable things can happen. The one important feature that was fixed is that before, if you saved a custom puzzle, it's almost guaranteed it wouldn't load up correctly. This was fixed by changing the format the application saves puzzles in, with the unfortunate side effect that any saved games you had before the change will fail to load. This problem will only happen with thsese two or three puzzles of yours that were saved in the old format.

January 11th, 2007 Disabled Timer Now Stays Disabled Across Sessions

A lot of people don't like the timer to tick away while they're playing because it makes them anxious. That's understandable—that's why Online Sudoku has long had the ability to disable the timer by clicking on it.

The problem was, every time you visited the page or loaded a new puzzle, you had to disable the timer again. Now, the state of the timer is remembered as an option. That means that if you're a registered user your timer will stay enabled/disabled on all the computers you use, or, if you're not a registered user, that it simply will remember how you set it before every time you load the game.

More hints were added to the hint system (which now shows up every few minutes under the grid). In the near future, expect the ability to change how often you get new hints, or even turn them off completely.

January 4th, 2007 Statusbar and Hints Added, Bug Fixes

It's been a long time coming, but finally Online Sudoku has a built in statusbar that will help users learn about Online Sudoku features and use them effectively. Every few minutes, a new hint will show up in the statusbar below the game. These hints will show you how to do things you may not know how to do, and will lightly encourage you to register if you have not already.

Getting this statusbar feature working was, well, a lot of work. Hopefully, however, you'll agree that it's worth it— it is quite pretty. Also, now that all the heavy lifting is done, it's easy to add new hints, so expect many more helpful hints to be entered into the system in the coming weeks.

There are a handful of small bugs remaining in the statusbar; these will also be fixed in the near future. Also, the statusbar will, in the near future, be modified to also show error messages and other important bits of information. As always, please contact us with any features you'd like to see added, or with any comments of any kind.

November 23rd, 2006 IE7 Support Added, Lots 'o Bug Fixes

If you're one of those people that insists on using Internet Explorer, and you've been pushed the IE7 update by Microsoft, consider yourself in luck. IE7 adds some nice features (nothing approaching what Firefox has to offer, of course) that make Online Sudoku look better than ever before on Internet Explorer. There's one down-side, however. IE7 has this cool feature that allows you to zoom in on any web-page — not just change the text size, but change the size of everything. That's cool, but it means that there's a new key combination that web applications like Online Sudoku can't use: Ctrl + + and Ctrl + –, which are used to add all valid marks to all spaces, and remove all invalid marks from all spaces, respectively. Now, if you're using IE7, you'll have to use Alt + + and Alt + – instead (people still using IE6 can use the old shorcuts just fine). The Shortcuts panel has been updated so if you're using IE7 it will tell you exactly what commands to use.

Of course, that's not all. This update also includes one big grab bag of bug fixes. Here are some highlights:

• Fixed Design Mode Bug For a long time now, there was a bug that messed up the game when you tried to move into design mode, to enter your own custom puzzle. That's now fixed.
• Share Button No Longer Valid During Design Mode For a while there, you could share puzzles while you were in design mode which, of course, didn't make any sense. The share button is now locked during design mode. (Remember, the Share button is hidden in the more options section of the control panel. Hit the little arrow above the timer to expand it.)
• Fixed Bug Where Difficulty Wouldn't Be Remembered Across Sessions For those of you who are registered users, there used to be a bug that occured about half the time, where when you logged in, the difficulty you had selected last time wouldn't show up. That's been fixed. For those of you aren't registered users, you should really consider it—it allows you to play your saved games on any computer!
• Can't Share A Puzzle That's Already Solved Another bug with the share button. It used to be possible to share a puzzle that you had just solved, which didn't make much sense. Now, like the Save button, the Share button will yell at you if you hit it when the puzzle is solved.
• Recent Scores Don't Show Up On Top Scores List Most of the time, when you solve a puzzle in record time, your time wouldn't have showed up on the top scores list. That had to do with a problem where the game was telling the server about your time right after asking it for the top scores list. The server didn't know about your time yet, so it couldn't put it on there. That's been fixed now, and your fast score should show up if it's fast enough to be on the list.
• Can't Be Logged In At More Than One Location It used to be possible to be logged-in at more than one location. This didn't make much sense because then your saved games and options on the server could get all confused. Now, if you log in somewhere else, you'll be automatically logged out at the other locations, and it will alert you of that fact. Just log in before you solve the puzzle to ensure that your name gets on the top scorer list!

There are a bunch of other bugs, of course, but those haven't been fixed yet. Look forward to a whole bunch of bug fixes relating to offline mode in the coming days. Also, look forward to a new feature that will help you learn about new features in the game, and also rewritten instructions (they're out of date, and don't have information about most of the coolest features).

October 31st, 2006 View Top Scores, Large Improvements To Puzzle Solved Dialog

Now, when you solve the puzzle, you'll be presented with a small, handsome dialog (no more of that alert window nonsense) that will show you the time it took you to solve the puzzle as well as the average time it has taken everyone else. What's cooler is that after a second or two a list of the five fastest solve times for that puzzle (and the users responsible for each record) will slide open. If you're in the list, you'll see your name highlighted in red.

Think you're pretty good at sudoku? Want your blazingly fast time presented to everyone else for the rest of time (or at least until someone else goes faster)? If so, then this is the perfect time to register. Registered users will have their name show up next to their scores—none of this anonymous "Guest" business. Registering takes only a second, and will let everyone else know that you're a sudoku master.

October 28th, 2006 Log In Screens Improved, Share Functionality Made More User-friendly

The log-in, change password, and register screens have been improved so they fade in and out, hitting the Enter key will submit the form, and hitting escape will close the form.

Also, the "share" feature has been made more user-friendly. Sharing puzzles is now even easier. Expand the options panel by clicking the "Options" button above the timer. Then, hit the "Share" button. If you want your friend to get a link to the puzzle exactly as you see it at that moment, check the box, and give them the link!

October 9th, 2006 Share Puzzles With Others

Gotten to a point where you get stuck and swear that there isn't a solution? Want to ask your friends for help? Now you can. The new 'Share' button, hidden in the options section of the control panel at the bottom of the grid, will provide you with a link to give a friend to pick up your puzzle exactly where you currently are. Or, if you want to brag about how quickly you solved a puzzle and bet your friends that they can't do better, you can send them a link that will let them start your puzzle from the beginning.

October 6th, 2006 Game Remembers Which Panels You Have Expanded

Now, the game will automatically remember which panels you have expanded, and re-expand them when the game starts up. Also, for first-time users the marks and numbers panels will now automatically expand, which should help new users figure out what's going on.

Now, the game remembers just about everything about how you left it. And don't forget that registered users will see all of their options load up when they log in on any computer, now including which panels are expanded.

August 25th, 2006 Logged In Users Can Access Saved Games Anywhere

Now, when you log in, your saved games and options follow you. Start a game at the office, finish it at home later that day. Essentially, you can bring your own copy of the game to any computer that has the internet. It's yet another reason to register.

August 22nd, 2006 Added Log-In Support

This update's been a long time coming. Now, it's possible to register a user-name, and login to play puzzles and monitor your progress. Although you can't view your records yet, in the near future you'll be able to see how you stack up against other players around the world. As soon as you register, it'll start recording your times, even though there's no good way to view them yet. And don't worry—you'll never have to show them to anyone else if you don't want to.

Also, in the near future, your saved puzzles will follow you wherever you login, so you'll be able to start up a game at the office and finish it a week later when you're vacationing on the French Riviera. Signing up only takes a second, so it's well worth it. Your e-mail address is only ever used to reset your password and verify your username—it will never be given out to any third party, ever. A more detailed and official privacy policy is on its way.

July 4th, 2006 Improved Off-Line Support

Today a whole bunch of user interface improvements to the recent off-line support feature were rolled out. Go ahead, give it a try – it intelligently handles most cases where you're disconnected from the internet with minimum fuss. It's not a feature that many people will use every day, but it's nice to know it's there if you need it.

What's perhaps more important is that now you can change how many puzzles to load up at a time. Just hit the "Options" button to slide out the options panel, where you'll now find a drop-down box where you can pick how many puzzles to pre-load. If you're taking a cross-country plane trip, bump that bad boy up to 20, wait a few seconds for the puzzles to load, and you're good to go. Keep in mind, of course, that you've got to have an active internet connection to pre-load new puzzles – waiting until you're on the plane to pre-load 20 ideas won't exactly be very effective. Your selection of playable sudoku puzzles will last longer than your battery.

July 2nd, 2006 Added Better Off-Line Support

This application uses this cool asynchronous request feature to load new puzzles. The good thing about that is that you never have to reload the page to get new puzzles. The bad thing? Well, there isn't really a bad thing, except that if you're disconnected from the internet, you're out of luck – you won't be able to get any more puzzles. In other words, you can't play Online Sudoku on an airplane.

Until now, of course. By default, the application now loads up five puzzles automatically. That means that once you load the page (and wait a couple of seconds), you'll have five puzzles ready to go, no matter if you disconnect your internet or not. After the five, of course, you'll need to reconnect to get more. And if you switch difficulties, all of the loaded puzzles will be thrown out. I know, it's not perfect – yet.

Now that the dirty work to implement this new feature is all done, it's all a matter of user-interface improvements. In the next few days, this feature will be made far more user-friendly, with options specifiying how many puzzles to keep loaded and warnings if you're disconnected from the internet and change your difficulty, among other improvements.

Oh, and more new puzzles have been added since the last update, but that's to be expected.

June 26th, 2006 Tweaked Styles, Added New Puzzles

Okay, so in comparison to the 17th's update, this one qualifies as a "non-update." But it's still useful. If you're playing on a computer that doesn't have good font smoothing – for example, 90% of windows computers – then it can sometimes be hard to tell when the marks list in invalid. Not to mention that those marks are pretty darned tiny. Who wants four marks in a row when you can't even see them? Now, whenever marks – or the actual number – are invalid, they'll be bold, too. If it doesn't pop right out and smack you in the face as soon as you make something invalid, then you might want to get your eyes checked out. Oh, and marks are now slightly bigger by default.

In addition, about 30 more puzzles have been added, including far more on the Intermediate and Advanced levels. Expect more in the coming weeks.

June 17th, 2006 Added New Auto-Save Feature

Even though the game used to warn you upon exit if you hadn't saved your game, I know some of you still lost your progress somehow or another. Well, those times are over (and let's not kid ourselves: that pesky "Do you want to save your progress?" when you quit was pretty annoying).

The new auto-save is approximately 15532 times better than the old auto-save. It automatically saves the puzzle every 5 seconds if you've made changes since the last save or auto-save. And the best part is, it won't overwrite the saves you do manually. Because the saved game and the auto-saved game are kept separate, there's no more annoying warning when you quit – when you navigate away from the page it just auto-saves, well, automatically.

Now that there's the potential to have two separate saved games – the user-saved game and the auto-saved game – how does loading a puzzle work? Well, just like you'd think it would. If you hit the load button, it will automatically load the user-saved puzzle, unless the auto-saved puzzle was saved more recently – in which case it will let you choose which one to load. If there is no user-saved puzzle, but only an auto-saved puzzle, it will load that one, but let you know that it's loading an auto-saved puzzle. In other words, you never have to worry – it will load the right puzzle automatically.

Now, there's practically no way to accidentally lose your progress. Even if the computer crashes, you'll lose at most 5 seconds of work. Keep in mind that Opera users are still at a slight disadvantage; the game will auto-save every 5 seconds, sure, but it won't also automatically save at the precise moment you leave the page.

But wait, there's more!

Before, it used to be hard to figure out when the last time you saved was. Also, when you hit the save keyboard shortcut – which, by the way, is the letter "s" – there was no good way to ensure that it actually saved. Now, the "Save" button will be red if you've made changes since the last time you saved (but not since the last auto-save). The button will turn back to gray as soon as you successfully save. Keep in mind, however, that auto-save is always chugging along in the background, so even if you quit when the Save button is red, auto-save will have your back.

June 13th, 2006 Added Backspace, Ctrl + Backspace to Clear Spaces

Firefox and IE users, rejoice! You can now hit Backspace to clear a space of its number, or Ctrl + Backspace to clear the space of all of its marks. The good 'ole 0 and Ctrl + 0 combos still work, of course, but many people find the backspace combinations more intuitive. Never again will you get 75% done with a puzzle only to instinctively hit the backspace key to clear a space, losing all of your hard-fought progress.

Now for the bad news. Opera and Safari users are still stuck with 0 and Ctrl + 0; both browsers don't let applications like this one override the default Backspace = Back button behavior. If you're playing this game on Safari or Opera and you're used to playing it in Firefox or IE, beware! The instinctive combo that will now be reinforced is still just as dangerous as it always has been on those two stubborn browsers!

June 9th, 2006 Completed Move to New Server, Implemented MySQL Backend

Finally, the move from the fas.harvard.edu servers is complete, and sudoku is now entirely at home on the komoroske.com server!

This opens up all kinds of cool possibilities for online sudoku, in particular, the ability to use a MySQL backend on the server – a capability that was sorely lacking on Harvard's server.

Now, when you request a puzzle from the server, a sophisticated database serves one up randomly from a database far larger than what could have been done on Harvard's servers. You see, before, the server-side script essentially read a text file will all of the puzzles in it, then randomly returned one of those. That was fine for small amounts of puzzles and users, but the solution was the programming equivalent of using only duct tape and paperclips for all of your home repairs. The server can now handle far more users and – more importantly for you – more puzzles. Expect to see far more puzzles in the coming weeks! In addition, puzzles report back to the server every time they are loaded or solved, which can help us figure out which puzzles only say they're "easy". Expect the server to leverage all of this new information in the coming weeks!

June 6th, 2006 Fixed Puzzle Retrieval Bug In Internet Explorer

Fixed a bug where Internet Explorer users would only be able to play one puzzle of each difficulty. Surprise, surprise, it was another Internet Explorer bug that had to be worked around. Now, even if you use Internet Explorer, you should be able to play as many puzzles as the server can dish out.

May 28th, 2006 Start Off With A New Puzzle, Difficulty Remembered Across Sessions

Now, when you start up the application, it will start with a new puzzle fetched off the server – no more of this "Default Puzzle" nonsense.

Also, now the difficulty that you select is remembered across sessions. If you leave the game when the difficulty is set on Beginner, it will start back up that way, too.

Finally, a few bug fixes were made. If the server is not responding correctly, you'll only be warned once, instead of multiple times.

May 27th, 2006 Options Save Automatically, Timer Can Be Disabled

Made it so that the view options you choose (like Show Invalid Marks and others) will automatically stay the same across sessions. That is, set the option now, and forget about it (until you clear out your cookies, that is).

Also, made it so that clicking the timer's text will disable it while you're working, if it's distracting you. Any time you load a new puzzle or finish, it'll automatically start updating again.

May 21st, 2006 Site Redesign

Made the site not look like butt, and added all kinds of helpful text, like the guide to the game and the Worst Intro To the Rules of Sudoku Ever.