The Arc of Yesod

The Arc of Yesod
Titelbild vom Spiel
Game No.	535
Voting	6.00 points, 1 votes
Developer	Robin W. Tinman, Colin Grunes, Stuart Fotheringham
Company	Odin Computer Graphics
Publisher	Thor Computer Software, Firebird
Musician	Fred Gray
HVSC-File	MUSICIANS/G/Gray_Fred/Arc_of_Yesod.sid
Release	1985
Platform	C64, ZX Spectrum
Genre	Grafik-Adventure
Gamemode	Single player
Operation
Media
Language
Information	Series: Nodes of Yesod (Forerunner)

Description[edit | edit source]

The Arc of Yesod is an action-adventure game spanning 256 screens. There is no scrolling; the screens are displayed using a flip-screen technique. As astronaut Charlemagne "Charlie" Fotheringham-Grunes, the player explores a cave system beneath the surface of the planet Ariat, inhabited by various hostile creatures. The goal of the game is to collect a total of eight crystals within this labyrinth, gain access to a monolith inside the planet, and ultimately destroy it.

The Arc of Yesod is the second game in a two-part series centered on astronaut Charlie. It is the successor to "Nodes of Yesod", but requires no prior knowledge of that game. Of course, experience gained in the first game with controlling the astronaut and navigating the cave system is helpful.

Backstory[edit | edit source]

In the predecessor game, "Nodes of Yesod", astronaut Charlie fought his way to a monolith inside the moon that was broadcasting incriminating messages into space about the weaknesses of Earth's defense system. However, Charlie's mission to destroy and silence this object failed: at the last moment, its creators teleported the monolith back to its home planet, Ariat.

Since the monolith is a highly advanced spy computer now containing critical security information about Earth's defense systems, the inhabitants of Ariat must not be allowed to access its data under any circumstances: the information would enable them to conquer Earth. Therefore, immediately upon his return from the moon, Charlie is placed on a spaceship bound for Ariat with the new mission of finally locating and destroying the monolith in the cave system beneath the planet's surface.

He is supported by a "sphere" — a flying, armed sphere that Charlie can launch, control, and recapture. This sphere can engage some of the enemies with fire, open side doors to adjacent chambers, and ultimately destroy the monolith.

The complete backstory of the game — including a summary of Charlie's experiences in "Nodes of Yesod" — can be found in the inlay of the cassette.

Design[edit | edit source]

The lunar landscape and the cave system that astronaut Charlie must explore are richly detailed and well-coordinated in terms of color; the variety and mostly fluid animation of Charlie's enemies is impressive. Combined with the musical accompaniment, featuring a melody that remains pleasant and engaging even after extended play, "The Arc of Yesod" is a very beautiful and atmospheric graphic adventure.

Intricately detailed, but a dangerous place: The surface of the planet Ariat

Aided by his "sphere", Charlie runs and jumps through the cave labyrinth — or is teleported.

The spacesuit only protects against falls from low heights; a fall from a great height is fatal.

Graphics[edit | edit source]

The graphics are rendered in monochrome text mode (screen memory starting at address $0400, character generator for the scenes on the planet Ariat in grid lines 0-175 at address $2000, for the status display in grid lines 176-199 at $0800). Only a 256x168 pixel section is used to depict the cave system, and a 256x176 pixel section for the planet's surface. The transition from one screen to the next is smooth and typically takes 100-120 ms.

Astronaut Charlie is usually represented by two, and during a somersault even by three monochrome sprites (sprites 0-2). While Charlie is on the planet's surface, four of the remaining five sprites represent the satellite (sprite 3), the rockets launching from the craters (sprites 5-6), and the moon orbiting the red giant in the sky (sprite 7). Sprite 4 unnecessarily traces the already dark gray structures on the rocket crater in dark gray.

Since sprite 2 is only needed to represent the astronaut during a somersault, it can also represent Charlie's sphere in the depths of the labyrinth. Sprites 3-7 represent his opponents, sometimes grouped in pairs. All collectible items and the sphere's projectiles are represented by text characters.

Sound[edit | edit source]

Several two-part melodies accompany the various phases of the game. Individual events, such as encountering enemies or collecting objects, are also underscored by short sound effects or audio sequences.

Hints[edit | edit source]

"The Arc of Yesod" takes place in a vast labyrinth beneath the surface of the hostile planet Ariat, whose passages are initially partially blocked and thus inaccessible. Astronaut Charlie carries a "sphere" — a flying ball that can both fight enemies and, with well-aimed shots, open gates to neighboring screens at numerous points. Furthermore, teleporters are located at various points, allowing the astronaut to travel to otherwise inaccessible areas of the cave system (see the middle animation in the gallery in the "Design" section).

The actual objective of "The Arc of Yesod" is to collect eight crystals and use them to reach a monolith at the center of the planet. By doing this, the player fulfills Charlie's mission to destroy this spy computer before the inhabitants of Ariat can read its memory and use it to launch an attack on Earth.

There are also a total of 8 astronaut helmets in the labyrinth's corridors, each of which grants Charlie an extra life, provided he hasn't already reached the maximum of 9 lives. These helmets also replenish his supply of bombs up to a maximum of 6. With these bombs, Charlie can paralyze or remove some of his opponents from the current screen for a limited time.

Controls[edit | edit source]

All important settings are configured via the start menu.

"The Arc of Yesod" can be controlled either with a joystick in port 2 or with the keyboard. The selection between these two input devices can be made via a menu on the start screen before launching the game by selecting "4. START GAME". The following mapping then applies:

or every second key in the Z,X,C,... row (for example, : ): The astronaut or the sphere moves or flies to the left.
or every second key in the Z,X,C row (for example, ; ): The astronaut or the sphere moves or flies to the right.
or every key in the Q,W,E,... row: The sphere is activated; if the sphere is already active, it flies higher.
or every key in the A,C,D,... row: A bomb is dropped; if the sphere is active, it flies lower.
or every key in the 1,2,3,... row: Jump; When the sphere is active, it fires projectiles in the direction of movement.
ENTER : Pause (resumes with another press of ENTER )

If the joystick is in its resting position, pressing the fire button makes Charlie jump vertically upwards. However, if the fire button is pressed while the joystick is pointing left or right, Charlie jumps in his current direction of view, regardless of which way the joystick was moved. Analogous behavior occurs when using the keyboard. This not only takes some getting used to but also makes quick changes of direction while jumping impossible, as the astronaut must first be turned around before jumping in the opposite direction.

An additional mode of movement is available only in chimney-like rooms without platforms: If the fire button is pressed while Charlie is standing motionless at the bottom of a screen, he begins to paddle his arms and fly upwards. Before takeoff, he must ensure he is facing a side exit he intends to reach during the flight:

Paddling his arms vigorously, the astronaut reaches a higher side exit...

...but only if the starting point and direction of view are well chosen!

Screen Layout[edit | edit source]

Screen display. Charlie has just discovered the third crystal (key to the armored door to the Monolith's chamber).

Enemies[edit | edit source]

Most of the enemies that lurk for Charlie in the caves beneath the surface of the planet Ariat can be divided into two groups. The first group consists of adversaries who — sometimes across multiple screens — periodically travel a predetermined path and cannot be fought by Charlie. They are relatively large, some are elaborately animated, and they launch Charlie into the air if he comes into contact with them:

A number of other, less harmful enemies burst upon contact with Charlie, but in doing so they drain his energy or briefly disrupt the joystick controls:

The enemy astronaut steals one of the crystals our astronaut has collected. In this case, however, the crystal is not lost forever, but reappears elsewhere in the labyrinth and simply needs to be collected again. The monkey with flapping ears cannot be shot down and permanently drains Charlie's energy upon contact.

Enemy astronaut

Monkey with flapping ears

Sonstige Objekte[edit | edit source]

The following items have a special function. The sphere (left image in the gallery) uses its projectiles to fight some of the enemies and opens passages to adjacent rooms. A bomb, when placed by Charlie, provides protection for about 7 seconds; during this time, it paralyzes the enemy astronaut, causes harmless enemies to explode, and prevents them from respawning.

Sphere

Bomb

Reaching the monolith is ultimately the goal of the game. It is located in a room that can only be entered through an armored side door; this door only opens if Charlie is carrying all 8 crystals.

Monolith

Tips[edit | edit source]

The sphere can not only open gates to adjacent rooms, but also fight some types of enemies without taking damage itself. Occasionally, it is therefore advisable to let it "clear" the airspace.
The bombs can be used against annoying but harmless enemies, providing a few seconds of respite from the pests. However, they are much more valuable for blocking the enemy astronaut and thus preventing the loss of a painstakingly collected crystal. At least some of the bombs should therefore be saved for this purpose.

The sphere can be used to clear the path.

A bomb provides approximately 7 seconds of respite from the pests.

Upon contact with powerful enemies, Charlie is launched into the air.

Solution[edit | edit source]

To solve "The Arc of Yesod", simply collect the eight crystals, which then act as the key to the monolith's chamber. A well-aimed shot from the sphere then destroys it, successfully completing the game. Good local knowledge — both within the labyrinth and on the planet's surface — and practice controlling Charlie and his sphere are helpful in finding the crystals.

Successful completion of Charlie's mission.

Map[edit | edit source]

The following gallery shows the initial state of the labyrinth on the left, with example objects drawn in, before any passages between adjacent chambers have been opened by the sphere. The image on the right depicts the empty labyrinth with all passages fully revealed.

If the astronaut crosses the left edge of the labyrinth, he enters the room located at the same level on the right edge. Similarly, leaving the game board to the right leads back to the left edge. In particular, the surface of the planet Ariat appears to expand infinitely in this way; however, the rooms repeat every 16 transitions.

Plan[edit | edit source]

The following animation shows an example of the starting position of all objects to be collected (crystals in green, extra lives in white) as well as the location of the starting room (gray rectangle) and the monolith (yellow rectangle) in 60 consecutive games. Only some of the rooms are used for placing objects; these are randomly permuted before the start of each game. Normal paths are shown as double lines in this representation, while passages to be opened from the sphere are shown as single, horizontal lines. Single, vertical lines represent trapdoors.

Schematic representation of the labyrinth with the initial position of all objects in 60 consecutive games

Internal Data Structures[edit | edit source]

For developing custom trainer functions and for analyzing or manipulating the data used by the game, knowledge of the memory allocation and internal workings is helpful. The following table therefore compiles a range of information about "The Arc of Yesod".

Address	Content	Comments
$000B-$000C	Aktueller Raum	X and Y coordinates of the space currently displayed on the screen; value range 0...15. The planet's surface has a Y coordinate of 4, the underlying planes have Y coordinates 5...15. The planes with Y coordinates 0...3 are only accessible via teleporters.
$001C	Number of Lives	Value range 0...9
$002D	Current Room	Packed number (X-coordinate in the low nibble, Y-coordinate in the high nibble) of the room currently displayed on the screen
$00AD	Monolith Room	Packed number (X-coordinate in the low nibble, Y-coordinate in the high nibble) of the room containing the monolith
$00BB	Remaining Energy	Value range 0...63
$804C-$804D	Joystick Malfunction	2-byte counter (little endian) that counts down from $0280; The fault ends as soon as the high byte at $804D counts down to $00.
$84F5	Number of bombs	Value range 0...6
$9917-$991E	Crystals found	Color codes of crystals found so far ($00: no crystal, $05: green)
$A8EB-$A8FA	Rooms containing objects	Packed number (X-coordinate in the low nibble, Y-coordinate in the high nibble) of all rooms containing a crystal or an extra life at the start of the game
$A90B-$A91A	Objects	Type of object in the assigned room ($00: , $01: , $FF: already collected)
$B09A-$B0B9	Visited rooms	Bitmap; one bit is assigned for each visited room. set ($B09A Bit 7..0 = left 8 rooms of level 0, $B09A Bit 7..0 = right 8 rooms of level 0, $B09B Bit 7..0 = left 8 rooms of level 1, ...)

Cheats[edit | edit source]

In the CSDb there are Cracks with a Trainer function. Particularly noteworthy is the version "Arc of Yesod +16E" by Hackersoft with its numerous variations (first image in the following gallery).

>

Votes[edit | edit source]

Voting of the C64-Wiki users (10=the best vote):
6.00 points at 1 vote. You need to be logged in to cast a vote.
Commodore User	Graphics 4/5, Sound 3/5, Toughness 4/5, Staying Power 3/5, Value 3/5	Issue 31 (April 1986)
ZZap! 64	91% (Presentation 82%, Graphics 96%, Sound 83%, Hookability 92%, Lastability 91%, Value For Money 90%)	Issue 11 (March 1986)
Your Sinclair	9/10 (Graphics 10/10, Playability 9/10, Value for Money 7/10, Addictiveness 8/10	Issue 5 (May 1986)
ASM (Aktueller Software-Markt)	Grafik 9/10, Sound 6/10, Spielidee 4/10, Spielmotivation 4/10	Ausgabe 6/1986
Crash	89% (Use of computer 91%, Graphics 93%, Playability 92%, Getting started 91%, Addictive qualities 84%, Value for money 86%)	Issue 26 (March 1986)
Tilt	Intérêt 4/6, Graphisme 5/6, Bruitage 3/6	N° 30 (Avril 1986)
Sinclair User	4/5	Issue 50 (May 1986)
Lemon64	6.87	April 7, 2023 - 39 votes
Universal Videogame List	3.9/5	April 07, 2023

Critics[edit | edit source]

Stephan64: "The Arc of Yesod is essentially a remake of its predecessor, "Nodes of Yesod", with new graphics and sound. Those who enjoyed "Nodes of Yesod" will be happy to see a continuation of Charlie's adventures (and perhaps mourn the loss of the cute mole, who had to make way for a simple bullet). However, those who were already annoyed by the previous game's irritating controls and far too many bothersome enemies probably won't be too keen on a reunion. At least the bugs are a bit more subtle now... 6 out of 10 points."

Miscellaneous[edit | edit source]

Cover[edit | edit source]

Inlay[edit | edit source]

Cassette[edit | edit source]

Fastloader[edit | edit source]

The [1] cassette version of "The Arc of Yesod" uses the software fast loader "Novaload". During loading, the fast loader's startup message is displayed first, followed later by a game loading screen.

Bugs[edit | edit source]

If the astronaut starts flying at the far right edge of a room without platforms, he cannot reach the next higher rooms, but instead gets stuck in the border of a screen further to the left — fortunately, he can quickly free himself from this. And some passages open only one way after being shot by the sphere, forcing Charlie to squeeze through a wall — and being catapulted through the maze if he jumps:

An incorrect starting point causes the astronaut's flight to end in the background...

...and jumping from a half-open passage catapults him through the maze

On the surface of the planet Ariat, the sprite representing the astronaut is incorrectly given lower priority than the craters behind it:

Charlie is obscured by the craters even though he is walking in front of them

Screenshot comparison[edit | edit source]

In 1986, the game "Heartland" features a reunion with astronaut Charlie — however, he has since switched to the dark side of the Force and now fights as a servant of the evil Midan against the (player-controlled) good wizard Eldritch:

Astronaut Charlie

Enemy "Astronaut" in the game "Heartland"

Theme[edit | edit source]

The musical score consists of three two-part melodies that play during the display of the start menu, during gameplay, and at the end of the game. The following gallery shows these melodies in standard musical notation. For creative reuse, the sheet music is also available as a PDF document (File:ArcOfYesod PDF.pdf) and in ABC musical notation (File:ArcOfYesod.abc.txt).

Noise[edit | edit source]

Numerous events in the game, such as picking up an object or colliding with an opponent, are accompanied by short sounds from SID Voice 3. Sometimes this is done with the noise generator, producing a short hiss or pop, and sometimes with other waveforms. In the latter case, the characteristic sound results primarily from the precise frequency response. The following gallery illustrates this by plotting the temporal evolution of the pitch at a resolution of 0.5 ms (2000 pixels/s in the original resolution) on a musical staff diagram. The scale at the top and bottom of the diagrams is divided into 10 ms segments.

Not visible in this representation is the envelope that distinguishes, for example, picking up an extra life from using the teleporter (first diagram in the gallery). The stepped pitch curves are achieved by changing only the high byte of the frequency parameter (at address $D40F) during output; the low byte (at address $D40E) always has the value $00.

In this representation, natural notes are shown in their exact position; semitones are shown midway between their adjacent natural notes (for example, G sharp midway between G and A). For all other notes, the vertical position is determined by the exact interval of their frequency from the next higher and next lower natural note.

Video Recording[edit | edit source]

Longplay of "The Arc of Yesod" on the C64

Trivia[edit | edit source]

The game's authors attempted to make analyzing and saving the program code of "The Arc of Yesod" more difficult by using the identifier "CBM80" at address $8004 to simulate the presence of a plug-in module, so that when the computer is reset, it is not reset, but only the following ominous threat appears on the screen:

Not everyone who presses the reset button needs to be insulted and threatened...

Highscore[edit | edit source]

The following rules apply for entry into the high score list:

The top spots are reserved for players who have successfully completed the game. Within these spots, the timer value determines the ranking; the fastest player (with the lowest timer value) takes first place.
This is followed by all entries where astronaut Charlie did not successfully complete his mission, sorted in descending order by the percentage performance shown on the screen at the end of the game.

Ivanpaduano - 27% (02.10.2023)
Stephan64 - 18% (24.04.2023)
Nobody - 0 (tt.mm.jjjj)


	#2 Stephan64		#3 Nobody

Links[edit | edit source]

Magazine

Test Report No. 2021 on Kultboy.com
ZZap64 test report
Commodore User test report (p. 22)
Your Sinclair test report (p. 75)
ASM test report (p. 35)
Tilt test report (p. 41)
Crash Magazine test report (pp. 129)
Sinclair User test report (p. 56)