Origins of the shape discovery mechanic

Speleomorph has a unique puzzle mechanic for acquiring new shapes. This started as a non-interactive animation, but eventually it became central to the game design.

(There are some conceptual puzzle spoilers in this essay, and it will make more sense with the context of the final game, so please try playing Speleomorph before reading!)

I'm interested in the non-linear progress typical of a Metroidvania. Early on you will catch glimpses of areas you can't reach with your current move set. Later you gain the necessary moves and return to the earlier areas, resolving the tension and reaching new branches of the world. I signed up for the Metroidvania Month 16 game jam knowing I didn't want to make a combat system, which is the other major element of the genre. Instead I was focused on movement and exploration mechanics.

The theme of the jam was "shapeshifting", so I wanted new moves to feel like different forms of a single character, rather than items to pick up and use, or different characters to swap between. I stuck with the first character design I came up with, where the different forms would all be tetromino blocks. 1 This worked out well thematically: All forms are different configurations of the same four squares, which suggests that the character is a uniform substance that takes on new shapes. 2

I first imagined that new forms would be imparted by machines found throughout the cave. An animation would show a die stamping down on the block, leaving it with a new shape that would then be part of the repertoire. But these machines seemed wrong for the theme, and I'd thought of the player character as the only moving agent in the game. I developed it into a more natural scenario: The block enters a hot area and melts down, flowing through fissures, finally collecting and solidifying into a new shape further down in the cave. This was an interesting image, so I started planning out the animation.

Imagining a molten block flowing through a narrow passage, I was reminded of the movement in Snake, where the head moves and the tail follows along, changing shape without changing length. 3 This suggested giving control over the transformation to the player, who could form the new shape through a series of Snake moves! Allowing the player to make the moves gives a feeling of agency over the transformation, even if they are narrowly constrained to guarantee a specific final shape.

But what if I don't constrain it to a single narrow path? If the hot zone is wider, then the player can traverse it in different ways. They might need to solve a puzzle to exit the zone, or they might acquire different shapes depending on how they exit. I knew I was onto something when I sketched a puzzle requiring the player to re-enter the zone backwards to gain another shape. I think of these puzzles as the minibosses of Speleomorph, when you solve them you naturally unlock a new ability. 4

During development I thought back to playing Mushroom 11, where you move the fungus by reshaping it. These "Snake with gravity" puzzles are also more fully explored in Snakebird, which I had played on iPad but forgotten until players mentioned it after release. I usually try to avoid ideas I've already seen, so I'm glad that this time I didn't get hung up on precedent. Unifying movement and transformation became the core principle of the design, leading to the shape-to-shape movement that became the main mechanic of Speleomorph.

1. At this point I thought that each shape would have unique moves. Refactor (formerly Tetropolis) is a "Tetroidvania" that develops along these lines. Without the tetrominoes this idea also came up in many other Metroidvania Month 16 entries.

2. A few recent games handle a reshapable character with more style: Tetronimeow uses an adorable disjointed cat, while The Plumber Thing goes with body horror.

3. Of course the snake also grows as you progress in Snake. Players have suggested including that in Speleomorph, expanding into the pentominoes or beyond. I had decided that this was too complicated, as with rotation (see Tetronimeow for how tricky a rotation interface can be), and there was already enough to do with fixed tetrominoes for the small puzzle I was making. Growmi is a great "Snake with gravity" puzzle that's based on a grow-and-shrink movement mechanic.

4. I also thought that this could be used for fast travel by embedding hot zone pipes in the walls, accessible once you had a shape that could reach them, but the final world map was too small to need this.

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