Techniques

The tricks that made the genre possible.

How the interface evolved

Colour cycling

Nothing is redrawn: only the palette colours rotate. That is how 256-colour VGA cards animated water, fire and sky at almost no cost. Mark Ferrari turned it into art in Loom's backgrounds.

Dithering

With only 16 EGA colours, mixing pixels in a checkerboard pattern faked in-between tones. Turn dithering off and you will see hard colour bands.

Parallax

Move your mouse or finger over the scene

Several layers scrolling at different speeds create depth in a flat background. Distant layers move a little, near ones a lot.

Dynamic music (iMUSE style)

LucasArts patented iMUSE in 1994 (Michael Land and Peter McConnell). Music follows the action but waits for the end of the bar so the transition is seamless. Switch themes while it plays.

Walk boxes and scaling

The engine has no idea where the floor is: the designer draws connected walk boxes. SCUMM finds a path from box to box, and each box sets the scale at which the character is drawn, so it shrinks as it walks away. Click the floor.

Priority screen (Sierra)

AGI and SCI stored every background twice: the picture and a priority screen of depth bands. If the character's feet are in a band further away than an object, it is drawn behind it. In AGI, colours 0 to 3 of that screen also marked barriers, triggers and water. Move with the arrow keys or by clicking.

From CGA to VGA

The same real King's Quest V screenshot (VGA, 1990) reduced to each PC graphics mode: CGA showed 4 fixed colours at 320 × 200, EGA 16 colours and VGA 256 chosen from 262,144. That is why Sierra and LucasArts shipped EGA and VGA versions of the same game.

Design ideas that changed the genre

  • Parser. The player types commands such as GET LAMP. Total freedom and total frustration: guessing the exact verb was part of the puzzle.
  • On-screen verbs. SCUMM (1987) put actions in plain sight. No more guessing words: the mouse era began.
  • No deaths, no dead ends. In 1989 Ron Gilbert published "Why Adventure Games Suck": players shouldn't die by surprise or get stuck without knowing it. LucasArts made it a rule.
  • Dialogue trees. Picking lines instead of typing them turned conversations into puzzles and comedy.
  • Cartoon logic. Using a rubber chicken with a pulley isn't logical, but it fits its world. Humour justifies the puzzle.
  • Pre-rendered backgrounds. 3D characters over backgrounds rendered on workstations, as in Grim Fandango: cinematic detail on home hardware.
  • Choices with consequences. Telltale swapped puzzles for moral decisions and the famous notice that a character "will remember that".
  • Deduction. The recent wave (Golden Idol, Return of the Obra Dinn) asks you to reason and fill in blanks rather than combine objects.