X Letters is a game under X to improve your typing skill. It is inspired by the game let‐
ters(6) by Larry Moss and Brent Nordquist (which itself is inspired by the game Letter
Invaders, and ultimately by the famous Space Invaders).
The goal of the game is to destroy the words that fall down from the top before they reach
the bottom. To destroy a word, you must simply type it.
The game is organized in levels of increasing difficulty. Each level is divided into two
parts: a normal part and a bonus part. During the normal part, ordinary english words
will fall down (found in the system's dictionary, usually /usr/dict/words). During the
bonus part, the words are randomly generated from printable ascii characters.
If a word hits the ground during the normal part, you lose a life (you have five lives
initially), and the word disappears (but the others keep on falling). If a word hits the
ground during the bonus part, the bonus part simply ends, with no additional penalty, and
the game proceeds to the next level.
The normal part of a level ends when a certain time has elapsed. The bonus part ends when
either a certain time has elapsed or when a word has hit the ground. The normal duration
of a half-level is 600 time units, or 45 seconds (whatever the level).
Typing a word correctly makes the word disappear and scores you one point per letter, plus
five more points, plus another extra three points if the word was destroyed in the top
fifth of the window. This is the only way of gaining points: partially typed words are
not worth anything, and even moving to another level doesn't bring you points (this is
because even if you don't type anything you will go beyond the first level).
Short words fall faster than long ones. Unless otherwise specified at compile time, words
are not allowed to collide into one another. Therefore, when a new word appears, the game
makes sure that all the words below it fall at least as fast as it. The fall rate of the
words also increases with the level (it is, however, the same between the normal part and
the bonus part of the same level). The rate at which words appear is constant on a given
level, but it increases with the level.
A word is considered typed when the last printable characters that you typed since the
word appeared are precisely the letters of the word. This means in particular that it is
possible to ``kill two birds with one stone'' if one word ends with the letters with which
another one begins - in fact, if two identical words appear (an unlikely but not impossi‐
ble situation), you need only type one of them. To say things differently, if you type a
correct letter it will make your position in the word advance by one letter, and if you
type an incorrect letter, it will make your position move back to the last place in the
word that matches the characters you typed. The current position in each word is indi‐
cated by putting the already typed letters in a different color (normally red). Note that
a different behaviour is selectable at compile time with which a wrong letter will cause
all letters to be considered wrong (to make the difference obvious, consider the word
``abracadabrx'': if after having typed ``abracadabr'' you press an ``a'', the normal be‐
haviour will take you back to ``abra'' whereas the alternate behaviour will take you back
to the beginning).
The game keeps a high score table. When the game is over, one way or another, xletters
will show, for the user and for the twenty best players, the name, the level reached, the
final score, and the time during which the game was running. Normally, each player is
allowed only one entry in the high score table. This can be modified at compilation time,
The top of the window shows three buttons. The Quit button will take you out of the game,
the Pause button will pause the game or resume it if it was already paused, and the Next
button will move to the next level (normal part). These buttons can also be accessed
through accelerators: the ``Escape'' key will quit the game, the ``Tab'' key (or ``Pause''
if you have one) will suspend it or resume it, and the ``Page Down'' key (or ``Next'' if
it is so labeled) will advance one level.
Three labels on the right of the buttons are used to indicate your lives, score and cur‐
Other than that, to play the game you must simply type the words. In order for the typing
to be effective, your mouse cursor must be in the game space (the large square area below
the buttons and labels). If you start typing while the game is paused, it will automati‐
Scoring is made much more complicated if you choose to use the Next button to warp through
levels. (The point is that it should be used to avoid having to go through all the easy
levels if you already type very fast. So it should not handicap you excessively by giving
you no points which you would have gotten if you had worked your way through those levels.
On the other hand, it should not be an obvious way of gaining arbitrarily many points.)
Here is the way it works: when you use the Next button to warp to the next level, you gain
350 ``virtual'' points. Those points are indicated in parentheses after your real points
in the score label. They are not worth anything by themselves. On the other hand, if you
have virtual points, every time you gain some points, that many virtual points will also
be converted to real points (until you no longer have virtual points). Thus, virtual
points are worth something only if you prove yourself good enough to make them so.
There are some restrictions to the use of the Next button. First, it will only work in
the bonus part of a level, or if no word has fallen lower than the top fifth of the
screen. This is so you can't use it to get yourself easily out of a tricky situation.
Second, if you already scored some points on the current level, using the Next button will
award you fewer than the normal 350 virtual points (see above), in fact precisely twice
fewer than as many points as you gained on the level (but no less than zero, of course).
xletters has a training mode, which you can invoke using the -train command line option.
In training mode, only one (english) word appears at a time, anywhere on the game space,
and it does not fall. A new word appears as soon as you finish typing the previous one.
In training mode, there are no lives, points, levels, or bonus words.
DEATHMATCH AND DUEL
xletters also has the amazing ``deathmatch'' mode. To invoke this mode, use the -death
command line option. This has the following effects on the behaviour of xletters: first,
it will read words on the standard input, and make them fall. Second, you can choose
between typing falling words, or typing a special word in a special part of the display,
just above the game space. To switch between both modes, use the Mode button or press the
``Backspace'' key. The special word typed must be an english word: if the letter you type
makes the word fragment no longer begin a word in the dictionary, it immediately disap‐
pears. When you type a full word, you can then send it by using the Send button or by
pressing the ``Return'' key. The word sent gets printed on the standard output.
These features make sense when two copies of xletters are run in deathmatch mode, with the
standard output of each being sent to the standard input of the other (possibly across the
network). Then the player on each game can not only kill his falling words but also send
words to the other player.
Even more extreme than the ``deathmatch'' mode is the ``duel'' mode, activated through the
-duel command switch. In duel mode, the computer does not send words of its own, and only
words sent through the standard input will appear. In this case, there is no Next button,
and switching to the next level can only occur after a certain amount of time. In fact,
there are no bonus parts of levels, so levels change twice more rapidly than in normal
play. Moreover, a level change does not erase all the current words contrary to what hap‐
pens in normal (or deathmatch) mode.
The X Letters distribution includes a shell script named xletters-duel which uses Avian
Research's netcat program (nc) to open a socket, run xletters in duel mode, and try to
connect to the same socket on a given computer. Thus, two people on two different comput‐
ers can play a duel by each running xletters-duel with the name of the other's computer as
parameter. (Both copies must be run within five seconds of the other.)
X Letters recognizes all the standard X Toolkit command line options, among which the fol‐
Specifies the background color to use.
Specifies the foreground color to use for the labels and buttons.
Specifies the font to use for displaying the labels and buttons.
Specifies the application name under which resources are to be obtained, rather
than under the default executable file name. name should not contain ``.'' or
Specifies the window title string.
Specifies the preferred position of the window. Specifying a size is not recom‐
Specifies the X server to use.
Explicitely give a resource string.
The following additional options are recognized by xletters:
Specifies the font to use for the falling words. (Sets the wordFont resource.)
Specifies which color to use for the words. (Sets the wordColor resource.)
Specifies which color to use for the correctly typed part of the words. (Sets the
Specifies which color to use for the background of the game space. (Sets the
Do not go in training mode (this is the default). (Sets the trainingMode resource
-train Run the game in training mode (see TRAINING MODE above). (Sets the trainingMode
resource to ``True''.)
Do not run in deathmatch or duel mode (this is the default). (Sets the deathMode
resource to ``normal''.)
-death Run in deathmatch mode (see DEATHMATCH AND DUEL above). (Sets the deathMode
resource to ``death''.)
-duel Run in duel mode (see DEATHMATCH AND DUEL above). (Sets the deathMode resource to
In addition, xletters recognizes -help and -version options.
groundBox (class Box, parent (toplevel))
This is the main application box that supports all the other widgets.
label (class Label, parent groundBox)
The xletters label. The text of this label cannot be changed.
quitButton (class Command, parent groundBox)
The Quit button.
pauseButton (class Toggle, parent groundBox)
The Pause button.
livesLabel (class Label, parent groundBox)
The lives label.
scoreLabel (class Label, parent groundBox)
The score label.
levelLabel (class Label, parent groundBox)
The level label.
gameSpace (class Core, parent groundBox)
The game space in which the words fall. Key presses and Expose events are handled
through event handlers and not the ordinary translation/action mechanism.
In addition to the resources of the various widgets, the xletters application itself rec‐
ognizes some resources. These are:
wordFont (class Font, type FontStruct)
The font in which the falling words are written.
wordColor (class Foreground, type Pixel)
The color in which the (untyped part of the) falling words are written.
typedColor (class HighlightColor, type Pixel)
The color in which the typed part of the falling words are written.
deathMode (class DeathMode, type String)
Either normal, death or duel according as the game should be run in normal, death‐
match or duel mode (see DEATHMATCH AND DUEL above).
trainingMode (class TrainingMode, type Boolean)
Whether the game should be run in training mode (this overrides any value of the
deathMode resource (see TRAINING MODE above).
(If not overriden at compile time)
The dictionary of words.
The high score table.
None known. Surely a very temporary situation :-)
This is one of the ugliest programs I ever wrote. I would not be surprized to discover
plenty of bugs in it. Version 1.0.0 was ugly enough. Version 1.1.0 gave a whole new
meaning to the word ``uglyfication''.
xletters wants to access a high score table. If this score table is to be shared between
several users, xletters will probably be made sgid games or some such thing. Beware that
it is probably very easy to fool (or even brake to pieces). I have no doubt that running
it against a fake X server (and probably other similar things) can give not-too-hard
access to whatever permissions it has been given. Consequently, it should not be given
any critical permissions.
Peter Horvai (@ens.fr) wrote the deathmatch feature and implemented mmap()ing
the dictionary file.
David Madore (@ens.fr) wrote version 1.0.0, all the X Windows parts of the
game, and this man page.
GNU public license. See the file COPYING for more information.