The characters
The contestants had to complete a number of tasks in order to achieve their overall goal (e.g. regain their crystal and return to their ship). Many tasks involved the drogna, a small transparent plastic disc containing a solid geometric figure, which was the currency of Arg. The value of a drogna was its numbered position in the visible spectrum multiplied by the number of sides of the figure. For example, a red circle is worth one unit, an orange circle is worth two units, a red triangle and a yellow circle are both worth three, and so on.
Tasks which often appeared included:

A simple computer game where Dogran, a Liverpudlian-accented 'dog', had to be guided around a 3D maze.
Belts around the contestants' waists attached to cords tying them to the wall; there was a predictable function governing the maximum distances of all the cords, which had to be discovered by induction.
The Drogna Game, which came in the middle of the programme, giving the contestants their opportunity to regain the crystal. The game is played by two players: one would be a contestant and the other would be a creature known as the Red Salamander of Zardil. This game became so popular that Acornsoft released a version for the BBC Micro home computer.

• The floor is marked out with symbols similar to those described above on drognas; the players stand at opposite sides of the board, and the crystal is placed in the centre.
  There is a rule determining whether a user is allowed to move from a particular drogna to another drogna. (One common example is: A player may move to any drogna with the same colour or shape as the one on which they started the turn. For example, you may move from a red triangle to any red shape or a triangle of any colour.)
  A player may only move to an adjacent drogna. However, a player may move across multiple drognas in one turn provided they all meet the given criteria. Hence, the drogna on which the player started the turn is not necessarily the drogna they have immediately left.
  If a player breaks the movement rule, the crystal retracts such that it cannot be taken.
  If a player becomes adjacent to the crystal and it is not taken or retracted, the player may take the crystal.
  If, during the move of the player not carrying the crystal, that player can legally step onto a drogna currently occupied by the player holding the crystal, they may take the crystal from their opponent. This is known as the Hargreaves Rule.
  A player wins by reaching the edge of the board while carrying the crystal.
  How many Argons around the pond. This was a game played just before the Vortex (possibly a time filler, if the contestants completed the whole game too fast, as it was not always played every show) The winner(s) (everyone had a chance to win) received a Green Cheese roll to triumphant fanfare. This Green cheese roll was of use when playing the Vortex (see below). Gandor would compere the game, it would start on a table with a number of drogna inside a velvet bag with draw strings. He would shake the bag and withdraw some drogna and place them on the table, then asking the first contestant "How many Argons are around the pond?" The contestants would start by adding the sides or points of the solid geometric figure that the drogna's had and fail to guess the right number. The key was that Gandor would place his fingers on the table top as he said "How many Argons are around the pond?" The number of fingers he would place down on the table would be the correct answer. Most people did not guess the answer or they would just happen to get it right by mistake.
  The Vortex (series 2 - 4). This was the last task in the programme. To return to their ship, the players had to jump between a grid of points, taking turns with the Vortex, another "player" (shown by a video effect generated pulsating column in series 2, and a computer-generated flashing column in series 3 & 4). If the human player jumped into the Vortex, it would explode and the human, who would lose the game, was said to have been "evaporated", meaning a long trip back home which had to be walked by foot along the interplanetary highway (Earth is a long way from Arg!). The important difficulty was that the human player could not see the position of the Vortex on the grid. Players would sometimes be permitted to buy Green cheese rolls or food with their leftover drognas, and this food could be thrown onto suspect squares to test for the presence of the Vortex. Players would sometimes put their Arg Crystal down to test the suspect square, except the Arg Crystal was never evaporated and not a good indicator of the vortex's position. Milk used in this way would, of course, become evaporated milk. Common tasks
  Where known, and applicable, the contestants are listed below in the order in which they played the Vortex game: [E] = evaporated, [S] = survived, [n/a] = didn't play.
  
  Episodes
  Originally broadcast in 1980 on BBC1 on Saturday mornings. Repeated in 1980 on BBC2 on Saturday mid-afternoons. Note: The final game of series 1 was not the Vortex - The travellers had to recross a grid of different coloured shapes in a particular path or they would be "vapourised". Where known, the contestants are listed in order in which they crossed and if they were Vapourised [V] or Survived [S].
  
  Episode 1: 24 May 1980, 9:29am-9:55am (repeated 27 September 1980, 3:12pm-3:38pm); 26 minutes; Elizabeth Estensen [S], Fred Harris [S], Mark Dugdale [S]
  Episode 2: 31 May 1980, 9:32am-10:09am (repeated 4 October 1980, 4:30pm-5:07pm); 37 minutes; Liza Goddard, Michael Rodd, Stephen Cox
  Episode 3: 7 June 1980, 9:46am-10:23am (repeated 11 October 1980, 4:42pm-5:19pm); 37 minutes; Pat Cater [V], Maggie Philbin [V], James Burke [V]
  Episode 4: 14 June 1980, 9:35am-10:04am (repeated 18 October 1980, 4:00pm-4:29pm); 29 minutes; Denise Coffey, Dr. Garry Hunt, Toby Freeman [final game not played]
  Episode 5: 21 June 1980, 9:09am-9:54am (repeated 25 October 1980, 3:40pm-4:25pm); 45 minutes; Lesley Judd [V], Robert Malos [V], Paul Darrow [V] Series 1
  Originally broadcast in 1981 on BBC2 on Monday early-evenings. Repeated in 1982 on BBC1 on Friday late-afternoons.
  
  Episode 1: 2 November 1981, 6:04pm-6:49pm (repeated 28 May 1982, 4:53pm-5:38pm); 45 minutes; Graeme Garden [n/a], Carol Chell [E], Nicolas Hammond [E]
  Episode 2: 9 November 1981, 6:04pm-6:49pm (repeated 4 June 1982, 4:52pm-5:37pm); 45 minutes; Madeline Smith [E], David Yip [E], Derek Gale [n/a]
  Episode 3: 16 November 1981, 6:05pm-6:50pm (repeated 11 June 1982, 5:52pm-6:37pm); 45 minutes; David Singmaster, Sue Cook, Philip Sheppard
  Episode 4: 23 November 1981, 6:05pm-6:49pm (repeated 18 June 1982, 4:54pm-5:38pm); 44 minutes; Tessa Hamp, Nerys Hughes, Derek Griffiths
  Episode 5: 30 November 1981, 6:08pm-6:53pm (repeated 25 June 1982, 4:53pm-5:38pm); 45 minutes; John Craven, Bill Green, Kirsty Miller Series 2
  Originally broadcast in 1984 on BBC2 on Thursday early-evenings. Repeated in 1985 on BBC2 on Thursday early-evenings.
  
  Episode 1: 2 February 1984, 5:39pm-6:18pm (repeated 5 September 1985, 6:49pm-7:28pm); 39 minutes; Sarah Greene, Anne Miller, Richard Stilgoe
  Episode 2: 9 February 1984, 5:40pm-6:18pm (repeated 12 September 1985, 6:50pm-7:28pm); 38 minutes; Sue Nicholls, Duncan Goodhew, Emma Disley.
  Episode 3: 16 February 1984, 5:39pm-6:19pm (repeated 19 September 1985, 6:49pm-7:29pm); 40 minutes; Sandra Dickinson, Chris Searle, Adam Tandy
  Episode 4: 23 February 1984, 5:40pm-6:19pm (repeated 26 September 1985, 6:50pm-7:29pm); 39 minutes; Paul McDowell, Bonnie Langford, Christopher Hughes
  Episode 5: 1 March 1984, 5:39pm-6:18pm (repeated 3 October 1985, 6:49pm-7:28pm); 39 minutes; Janet Fielding [E], Nigel Crocket [S], Neil Adams [n/a - was evaporated earlier by the Rangdo when he presented His Royal Highness with salt, which annoyed him.]
  Episode 6: 8 March 1984, 5:40pm-6:25pm (repeated 10 October 1985, 6:49pm-7:34pm); 45 minutes; Fern Britton, Noel Edmonds, Ray Virr Series 3
  Originally broadcast in 1986 on BBC2 on Tuesday early-evenings. Repeated in recent years on the digital TV channel Challenge.
  
  Episode 1: 7 January 1986, 6:49pm-7:28pm; 39 minutes; Sheelagh Gilbey [S], Roy Kane [E], Ian McNaught-Davis [S]
  Episode 2: 14 January 1986, 6:50pm-7:29pm; 39 minutes; Johnny Ball [E], Barbara Lott [E], Liz Hobbs [E]
  Episode 3: 21 January 1986, 6:49pm-7:28pm; 39 minutes; David Sandeman [E], Fiona Kennedy [E], Ian McCaskill [S]
  Episode 4: 4 February 1986, 6:52pm-7:30pm; 38 minutes; Prof. Heinz Wolff [S], Deborah Leigh Hall [E], Ruth Madoc [S]
  Episode 5: 11 February 1986, 6:50pm-7:28pm; 38 minutes; Joanna Munro [S], Val Prince [S], George Layton [S]
  Episode 6: 18 February 1986, 6:49pm-7:28pm; 39 minutes; Heather Couper [E], Keith Chegwin [E], Adam Gilbey [E] (The broadcast of this episode was postponed from 28 January 1986 due to coverage of the Space Shuttle Challenger disaster.) Signature tune
  Master tapes of the following episodes no longer exist - the tapes were deliberately wiped by the BBC in order to reuse them:
  *Off air recordings of these episodes have been returned to the BBC (they would still be interested in obtaining better quality versions).
  
  Series 1, Episode 2 - Saturday 31 May 1980. Liza Goddard, Michael Rodd, Stephen Cox.
  Series 1, Episode 5* - Saturday 21 June 1980. Paul Darrow, Lesley Judd, Robert Malos.
  Series 2, Episode 2* - Monday 9 November 1981. Madeleine Smith, David Yip, Derek Gale.
  Series 2, Episode 4 - Monday 23 November 1981. Tessa Hamp, Nerys Hughes, Derek Griffiths.