Overview

LPath is a command line tool to validate stage transition path of a game. A typical scenario is when a platformer game has a non-linear stage traversal path, we must validate, that player can really reach the end-game stage. It is possible that player fail to finish the game with the following reasons:

1. A stage requires special skills to pass through. However the skills can't be retrieved in previous stages. Player are stuck when reaching this stage.
2. A stage leads to a circular path, forcing player to endlessly go through a path without reaching end of game.

I used lpath tool to validate my game design of my own game project, Tsetesg's Adventure.

Quick start

lpath is developed by (Zig programming language](https://ziglang.org). For now I use zig master branch, in order to manage dependencies with zigmod tool.

For Archlinux users, you may install zig and zigmod from AUR with command line below. Note that you may also need to install zls for LSP support.

yay -S zig-dev-bin zigmod-bin

## If you need LSP support
git clone https://github.com/zigtools/zls
cd zls
zig build -Doptimize=ReleaseSafe
cp ./zig-out/bin/zls ~/bin/zls

After installing correct zig and zigmod build, build code from command below.

git clone https://github.com/fuzhouch/lpath
cd lpath
zigmod fetch
zig build

A command line of lpath looks like below:

$ ./zig-out/bin/lpath --profile=./example.toml

The --profile command line argument reads a TOML file, which the information of each level. The computation logic interpretes TOML file, understand settings of each level, and print a list of path that player may go through. Thus, game developer can estimate whether there's any skills or path that can't be visited.

How does lpath work

Concepts

A game is modeled with the following basic concepts:

1. Stage. Stage defines minimal unit that player play through.
2. Exit. An exit leading to next stage. So player can move from one to another.
3. Skill. Skill defines prerequisite when moving to next stage from an exit. A skill is always unlocked when passing through a stage. An exit can require one or more skills to pass through to next stage.

Assumptions

With the concepts above, lpath introduces a model with the following assumptions:

• A profile defines one and only one game.
• A game includes a collection of stages.
• A game includes one or more stages.
• A game has one or more end-game stages.
• A game has one and only one begin-game stage.
• A stage has one or more next-stage exits. Each exit leads to one and only one "next stage".
• A stage can offer one or more skills after passing through. For example, a BOSS fight stage grants a new skill.
• A next-stage exit may require one or more skills to enter.
• Empty string ("") is a speical value because TOML does not allow empty array. It's not processed in lpath.

Below is an example:

[lpath]
skills = ["pan", "glide", "fireball"]

    [[stages]]
    id = "1-1"
    description = "outside-castle"
    begin = true
    next-stage = { "1-2" = [""] }

    [[stages]]
    id = "1-2"
    description = "castle-gate"
    next-stage = { "bossfight1" = [""] }

    [[stages]]
    id = "bossfight1"
    unlock-skills = [ "pan" ]
    next-stage = { "2-1" = [""], "1-1" = [""] }

    [[stages]]
    id = "2-1"
    next-stage = { "2-2" = [""], "2-3" = ["pan"], "2-4" = ["fireball"] }

    [[stages]]
    id = "2-2"
    end = true

    [[stages]]
    id = "2-3"
    next-stage = { "2-5" = ["glide"] }

    [[stages]]
    id = "2-4" # Unreachable due to skill unmatch in 2-1
    end = true

    [[stages]]
    id = "2-5" # Unreachable (2-3 is deadend)
    end = true