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The Forest - User Guide

A major aim of The Forest, from its earliest version around 1982, has been to help people interpret the contour information in maps. That enables orienteers to navigate without just following roads or streams, it helps hill walkers to avoid getting lost, and more generally it helps anyone reading a map to get the most out of it.

This program includes some non-trivial games and diversions for those who are not orienteers; we will call them explorers, which relates to another version published in the 1980s.

The Forest also demonstrates a technique for generating vast terrain by an algorithm rather than by storing it in memory or having to download it as a huge amount of data. It is written in JavaScript for an HTML5 web page and the program occupies only about 200 kilobytes, so it downloads and runs very quickly. Nevertheless it has more than 1,000 sq km of forest to explore (very much more!).

Try it: The Forest (


When The Forest has loaded you will see that there are buttons around the map in the main display area. The buttons are large to help those using tablets or phones with touch-screens but no keyboard. The buttons often indicate keyboard alternatives (for those who do have keyboards): either tap/click the button or press the key. Hovering over a button will sometimes show alternative keys that may also be used. Here is an example:

This button shows that when it is tapped/clicked you will move forward on the ground. It also shows that if you have a keyboard you could instead type the upward arrow key, []. The example was captured when a mouse was hovering over the button and that shows that another possibility is to type the [f] key. Not all buttons have keyboard alternatives.

There is another alternative to using any of the buttons which show an arrow key: instead tap or click just inside the corresponding edge of the map or scene display area. The top edge moves you forward in the scene or moves north on the map, and so on.

Occasionally explorers will find it relevant to use the [Enter] key and for those without keyboards the same effect is obtained by tapping/clicking the centre of the map/scene display area. Sometimes also it is useful to tap/click on an object in the scene. It should become apparent when these actions are needed.

 The initial map

When The Forest starts it shows a tiny portion of the map on which your position is marked with a red circle. The red circle is slightly pointed to indicate the direction in which you are facing. Initially you will be looking almost due south. The dashed red circle indicates how far you will be able to see around you on the ground, a distance of 60 metres when you start.

 The map colours & symbols

To the right at the top of the map is a key for understanding map colours and symbols. These are designed to be the same as are used internationally on maps for the sport of orienteering. It may seem surprising to some that the white areas are wooded. This is because open woodland (open rather than thicket) is the most ideal terrain for orienteering. It is reasonably fast to move through but you cannot see long distances.

Notice that every fifth contour on the map is thicker than the others. This is normal on orienteering maps. If you study the map you will see that this thickening helps to interpret whether some contours are up or down from neighbouring ones. (Orienteering maps also use downward-pointing tags on some contours to help further. There does not seem to be a way of doing this automatically and reliably by programming.)

Scale is given by the fact that the black north lines are 300m apart. 1 pixel in the display represents 1 metre on the ground. Actual size depends on the size of your display screen.

 The scene on the ground

The first thing you might want to do is tap/click the button at the bottom right corner of the map (or, as it suggests, type the [s] key) to view the scene from your position:

The scene view (below) indicates what you would see from an eye level 1.5m above the ground. The view indicates whether the ground ahead slopes up or down, according to the contours on the map. The type of terrain ahead is indicated by graphics. Real photographic images are used rather than simple drawn graphics. The ground is drawn in true perspective out to a certain distance ahead (the visible range). Initially this range is set to 60m but you can select greater ranges. See the Settings section for how to do this.

Switch back and forth between the scene and map to see how each corresponds to the other. If you have a keyboard you will find that you can keep pressing either one of the [m] or [s] keys to switch between map and scene.

Notice how the buttons change depending on whether you are viewing the map or the scene.

Next try turning from side to side and right round, so you understand how the scene changes and it still corresponds to the map. Take note of what the compass is showing, at the bottom of the scene (the red end points to north) and how that relates to your orientation as shown on the map. Left and right turns change your bearing by 15 degrees.

Then move forward in the scene. You will find that when you switch to the map you will remain in the centre of it wherever you have moved to.

It is possible to orient the map so that whatever your compass bearing is, the direction ahead of you will be straight upwards on the map. See the Settings section for how to do this.

On each step forward the bearing drifts by a random amount, up to 5 degrees to either side. In real life you would not be able to follow a set bearing precisely. However, this drift does not occur if standing on a paved area because paths (between buildings) are easier to follow.


When The Forest starts your role is that of Explorer. By all means stay in this role if you just want to explore and discover that there is a treasure hunt with map fragments, coded clues, and many other things to investigate. There is more about this later: see Explorers: games for you.

However, below the title of The Forest, under the left side of the main display area, is a drop-down list of other possible roles you could choose.


This box appears to the right of the screen. It contains various optional adjustments that affect the map and scene and your movement.

The settings dialogue

For the experimental settings see below.

 The status line

Below the map or scene, near the bottom of the HTML page, there is a status line which is rewritten every time the display changes. An example when a scene is displayed looks like this:

x = 15233.55, y = 5755.24, bearing 156°, steepness = 13, Drawn in 309ms (7309 images)

You may be interested to watch how the number of images and the time taken change as the visible range is altered via the drop-down control. They should go in proportion to the square of the range.

The status line is simpler when a map is shown, just giving x and y for the centre of the map and the time it took to draw.

If you make a note of them you can use the x and y coordinates to get back to any place in The Forest (but not if your role is orienteer, on a course).

 Two windows

On a PC (but not on a tablet or phone) you may well have room on the screen for part of the map alongside the scene on the ground. This can be achieved by having two browser windows open, each with a copy of the program running in it:

Map and scene side by side in 2 windows

 Optional URL parameters

It is possible to control some of the settings when The Forest first starts, by adding optional parameters to the URL (its internet address). This is done by appending a question mark (?) to followed by a number of "name=value" pairs separated by ampersands (&). For example,

This example would tick the "Max detail"check-box and set the visible range to 150m.

The full list of possible parameters follows.

 Explorers: games for you

The treasure chest

Explorers can see things in the forest which orienteers cannot (orienteers are not to be distracted). Some of these things will suggest a target to aim for (more achievable than in my 1980s Explorer version of this program: see Pixelatron). There is a treasure hunt which goes through several stages (game developers call them levels). There really is a treasure chest and many clues about where to find it.

Where orienteers would see a traffic cone, not marked on the map because it is potentially movable, explorers will find something else. Out in the open cones are replaced by aircraft that may be boarded to get aerial views. In woodland there are instead posters with writing on giving some clues for finding treasure. The clues are written in a code which the explorer will have to decipher. (This vocalian code was devised many years ago by Kevin Cook when we were school friends.)

A mine shaft

Also, explorers will fall down mine shafts if they get too close (orienteers are immune to this). There is an underground level to explore and it is possible to get back out again because there are some ladders. This is akin to dungeons in other games. There are things to find which can be useful in pursuing the treasure hunt.

NB: For explorers in certain situations the Enter key is significant (or on touch screens tap near the centre of the scene).

You will inevitably want to copy and save images of some of the things you see but this program does not provide any such facility. Instead you will need to use a screen copying program in whichever system you are running, such as the Snipping Tool in Windows.

Hint: there is a short-cut, described in this page, for something which may at first seem very lengthy in your task.

Hint: the target locations are within the first 32km block of the forest (the status line will show coordinates lying in these ranges: 0 < x < 32768 and 0 < y < 32768).

There are also several examples of a green door in a wall, to be entered to see a completely different view. Once again, there is a way back to the normal world but it may be difficult to work out.


There are buildings occupying definite 3-dimensional spaces rather than being merely flat photos. These are more of an obstacle to orienteers because it is not possible to just run across their patch of ground. Instead it is necessary to steer a path along the 4-metre-wide alleyways between the buildings.

The buildings are arranged in a regular grid arranged exactly north-south and east-west. They are shown on the map as black squares on a grey background indicating the paved area on which they stand.

A view of some buildings and the associated map

There is a door on every building but it may not be on a visible side. The doors are all different colours and have different key codes. It is possible to enter any building if you know the key code specific to its door. There are clues to help you determine the key codes. This will not be of any interest to orienteers but explorers following the treasure hunt will find the clues. There are things to find inside buildings and it is necessary to get inside a particular building before a certain stage of the treasure hunt becomes possible.

 Extra buttons/keys

Explorers can use some other keys to achieve certain effects. For those without keyboards there are some buttons shown to the right of the screen to tap/click instead.

When the map is displayed:

When the scene is displayed:

 It's raining

Something else which explorers can experience (but orienteers will not want to be bothered with) is changing weather. Rain causes the levels of lakes to rise. When it stops and the sun comes out, the levels fall back. A message appears briefly when lake levels are back to normal. This illustrates that the terrain can change. Earthquakes would change the topography more drastically and that could easily be programmed but it has not been done (yet).

 Aerial views

Where orienteers might see a traffic cone on open ground, those in the role of explorer will instead see a helicopter. When within 7m it is possible to board the helicopter and ascend to view the terrain from above. This gives a new perspective in more than one sense: by switching between scene and map it is then possible to get a different idea of the relationship between contours on the map and the relief of the terrain. It may be useful for orienteers to try this.

The helicopter can only land (reduce altitude to 0) on open ground. It remains where it lands and may be used again.

An example of an aerial view can be seen at the bottom of this page.

Interestingly (to programmers and mathematicians) the aerial view reveals patterns in the planting of trees, patterns which are not apparent at ground level. This is particularly the case for thickets because the tree images there are more similar to each other than in the mature wood. The patterns are reminiscent of those arising in cellular automata and will be a property of the algorithm used for positioning the trees, based on binary digits of multiples of pi.

 Orienteering: the courses

If you are not familiar with the sport of orienteering you may like to read this: British Orienteering Newcomer's Guide

When you choose one of the 3 possible orienteering roles (novice, average, expert) in The Forest you will be prompted to select which course to run, from a drop-down list:

Drop-down list of orienteering courses

 The easy short course

Map showing the short easy orienteering course

Notice the digital clock at bottom left which starts as soon as a course has been selected. You will be positioned just in front of the start, which is in the centre of the purple triangle symbol. When you switch to the scene you will see the start banner and you will be facing roughly in the direction of the first control point. Control points are at the centres of the numbered circles and they must be visited in ascending numerical order. The Forest program does not allow them to be taken out of order. The course ends at the double circle shown on the map, where there is a finish banner.

The second control point on the easy course Control card for short easy course

Control points have orange and white markers like this bearing a 2-letter code. You can check the code against a control card which appears to the right of the map/scene display. The card shows a description of the control, in this case a boulder, and whether you have visited it. This is the second control on the easy short course. The map shows how it lies on the edge of a wooded area with moorland beyond.

 Analysis at the finish

When an orienteer completes a course the full control card and a table analysing the route are shown:

A completed control card Results analysis table

There is also a button above the results table for causing the actual route taken to be plotted on the map. This also means that automatic reversion to the role of Explorer does not occur until the results are cleared.

It is possible to abandon a course part way round and still see the analysis for the portion completed.

How is it that the orienteer can sometimes complete a leg of the course by travelling less than the crow-fly distance? Easily because it is only necessary to be within 5m of a control for it to be punched. By approaching and leaving controls in the right direction it is possible to cover up to 10m less than the actual distance between controls. This is not just a feature of this simulation: it now happens in the real sport because electronic devices are used for automatic punching when within 5m of a control.

 The score event

Map showing the start and finish of the score event

This is part of the map for the start of the score event. As for other courses, the purple triangle is the starting position and the double circle is the finish. The numbers alongside the control circles are points which can be scored by visiting the controls (by getting within 5m). Scores are proportional to the distance of the controls from the finish point. You can choose which controls to visit, in any order. Once a control has been visited it cannot be used again.

There is a time limit. You must reach the finish within 1 hour. Otherwise there is a penalty to be deducted from your score, based on the number of seconds you are over the hour.

 Course planning

As well as the permanent courses supplied with The Forest, orienteers can make their own. Furthermore there is a facility for such courses to be sent to others to plug into their copies of The Forest. These courses are held within each user's own browser; nothing is sent to the server.

The point is that a team trainer can plan courses and send them to team members to try on their own machines.

On selecting the role of course planner, two buttons appear: either a new course can begin to be planned or a new web page can be opened for managing the available courses.

 Making a new course

The first button, to begin a new course, further changes the page to provide other buttons, which remain visible whether the map or the scene is being viewed.

The options are as follows. The map is redrawn with course symbols as the course is built up.

You would then change to another role to complete the course planning process.

 Managing courses

This button takes you to a new web page that lists existing courses and allows several things to be done with them.

The first few courses listed are the fixed ones that are supplied as part of The Forest. Then your own courses are listed. There are 3 possible actions for these lower rows of the table:



When in the role of Engineer, displaying the map, clicking anywhere on the map causes this menu to appear over the top left corner of the map. It should be self-explanatory. As you click on further points and extend the road it appears on the map.

It is important to note that the road will not appear in a ground scene until the "End road here" button has been used. That button also leads to a choice as to whether to save the new road so it appears in subsequent runs of the program. The data are only saved locally in your browser.

If a road crosses a lake, which is perfectly permissible, it will appear in scenes as a crude form of bridge, just supported by wooden posts.

You, the engineer, should be positioned in the visible part of the map when clicking points for new roads because otherwise clicking one of the buttons in the menu (except the first and last ones, start and cancel) will cause the map to redrawn, centred on you.

It can be amusing and educational to try linking towns by roads that tend to use the contours rather than going straight up or down steep hills. Then go along the roads on the ground to see how that has worked.


 Plotting the terrain in 3D

This is a weak feature of the program and it may disappear in later versions.

The aim of the 3D plot is to help people interpret contour lines on the map. It may take several seconds to draw the plot - rather longer than the scene or map views.

The following is a version of the map showing the area of a 3D plot. This can be seen by selecting this map kind in the settings.

Map showing area of a 3D plot  

 Latest changes & development

Recent and planned changes are summarised on the "What's new" page. I am open to ideas for further enhancements.

 20.3.28: Streams and paths

There are two new kinds of features in the terrain. They are both experimental, so users may choose whether to switch them on, by ticking boxes in a new "experimental" section at the bottom of the settings area.

Map showing streams


Some water holes (ponds) have streams flowing downhill from them. Some end in lakes, others in marshy areas.

These streams often help with contour interpretation: is a contour uphill or downhill from its neighbours? They may therefore be a useful educational tool.

The streams have a tendency to run on 45° bearings and you may think they tend to be too straight. In real forests drainage ditches are often dug like this.

The longest streams I have found so far are about 400m long.

The representation of streams in the scene view is very basic and will need improving; it does not yet indicate when you are standing in a marsh.

The streams also have some undesirable properties, which is why they are still experimental:

The previous Water (key w) button, to make a stream from the observer's position, has been removed.

Map showing a path


These are less successful than the streams but they represent a major breakthrough in the programmatic generation of the terrain because it was previously thought impossible to do this automatically.

Paths are shown on the map as grey lines of varying width, sometimes with blobby areas. In the scene they appear as rather badly placed paving. It is extremely difficult to see how they could be converted automatically to conventional dashed lines on the map and so paths must also remain experimental.

 Further information

There are some pages about my orienteering maps of real forests here. Follow the links there to read more about the maps for the original ZX Spectrum simulation of orienteering.

In particular there is a page about why The Forest is designed the way it is, which I wrote in the mid-1980s. It still has some relevance, especially about why I do not attempt to use maps of real forests (a scarce resource in the UK).

I started developing the new HTML5/JavaScript version in 2014 but it was heading more towards my second Spectrum program, Explorer (published by Electric Dreams in the mid-1980s). The new version included the possibility of falling down mineshafts and navigating underground. It also included a teleportation feature whereby typing a string of characters would take you to a new position on the map, seemingly at random but the same string would always go to the same place. Having got those features to work I shelved the project for a while.

My interest began again in February 2018 with an email out of the blue from Graham Scott of NATO (Newcastle and Tyneside Orienteers). He and I had been members of Tyneside Orienteers (as it was then) more than 30 years ago. I decided to complete the program as a purely orienteering project but it soon developed into much more than that.


Try The Forest:

Detailed history of The Forest (the next page here).

A 1984 review of the original version, in Crash magazine.

A programmer's guide to The Forest is also being written.

If you wish to learn to program you could do worse than follow my JavaScript course, based on training I used to give professionally.

British Orienteering Newcomer's Guide

Better Orienteering - a site containing a huge number of references and links to useful orienteering resources.

My own orienteering maps

Food for thought: Philosophy of The Forest

 View from a helicopter

Finally, here is an example of what can be seen as an explorer if you find a helicopter, go up in it and fly around for a while. Notice how the helicopter controls appear, top right.

A view of The Forest from a helicopter
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