# Moonfall

Moonfall is the name of a game engine that I spent several months developing back in 2008. It leveraged
[SDL](https://www.libsdl.org/) for graphics, [Lua](http://www.lua.org/) for in-game scripting, and
[wxWidgets](https://www.wxwidgets.org/) for the built-in developer tools. The cross-platform engine was written using
[Code::Blocks](http://www.codeblocks.org/) IDE, but Visual Studio project files are also available.

The inspiration for the game came partially from the [Harvest
Moon](http://en.wikipedia.org/wiki/Harvest_Moon_%28video_game%29) video game for the Super Nintendo and from the [When
They Cry](http://en.wikipedia.org/wiki/Higurashi_When_They_Cry) by [07th
Expansion](http://en.wikipedia.org/wiki/07th_Expansion). The protagonist is a city dweller, who upon inheriting a small
farm from a distant relative decides to try his hand in agriculture. He finds the residents of the nearby small town a
friendly bunch, but something about them does not seem right. Everyone is appears to be hiding something from the
player, who must uncover the truth to survive. In short, this is (as I have described it to my friends), "Harvest Moon
with murder."

From a technical point of view, the game engine was an exercise in creating a completely data driven game. In
retrospect, it was probably over-engineered, but in general it was flexible and I liked what I could do with it. At the
core of the engine was the `Actor` class, the functionality of which could be expanded through add-on properties. The
property definitions were specified in XML; for example, below is the definition for the playable character:


```
<Actor alias = "Player.01" dynamic = "1" layer = "4" thumbnail = "Player.01.Idle.S.01">
    <Properties>
        <Animation />
        <Script resource = "Player.01.Default" />
        <Physics />
    </Properties>
</Actor>
```

In addition to the self-explainable `Animation` and `Physics` properties, you can see a `Script` node which associates a
Lua script with the actor. Scripts would get notifications about events such as `OnActorUpdate`, during which custom
processing could take place:


```
function OnActorUpdate(elapsed)
    if InputIsKeyTriggered(META_KEY_USE) then
        DoActorUse()
        return
    elseif InputIsKeyPressed(META_KEY_UP) then
        DoActorWalk(DIRECTION_NORTH)
        return
    elseif InputIsKeyPressed(META_KEY_DOWN) then
        DoActorWalk(DIRECTION_SOUTH)
        return
    elseif InputIsKeyPressed(META_KEY_LEFT) then
        DoActorWalk(DIRECTION_WEST)
        return
    elseif InputIsKeyPressed(META_KEY_RIGHT) then
        DoActorWalk(DIRECTION_EAST)
        return
    end

    DoActorIdle(playerDirection)
end
```

Scripts can directly interact with properties on the parent `Actor` and can communicate with surrounding world via a
messaging system. This made it possible to build any game object imaginable by editing a couple of XML files and some
simple scripting.


```
function DoActorWalk(direction)
    if playerAction == ACTION_WALK and playerDirection == direction then
        return
    end

    ActorPhysicsSetVelocity(playerId, playerWalkVelocities[direction])
    ActorAnimationSet(playerId, playerWalkAnimations[direction])
    ActorAnimationPlay(playerId, true)

    playerDirection = direction
    playerAction = ACTION_WALK
end

function DoActorUse()
    actorsIds = ActorPhysicsQueryShapeCollisions(
        playerId,
        ACTOR_SHAPE_TYPE_COLLISION_INTERACT
    )

    for i, v in ipairs(actorsIds) do
        ActorScriptSendMessage(v, "interact", { user = playerId })
    end
end

```

I eventually stopped work on Moonfall due to a lack of time, combined with the fact that I am not an artist and could
not author the assets required to develop this into a complete game. The full [source
code](https://github.com/FooSoft/moonfall) is available on GitHub; below are some screenshots of the game and built-in
tools.

## Screenshots ##

![](index/gameplay.png)

![](index/sprite_editor.png)