Mods

The rules a script lives by

• Runs where the world runs

  Scripts run wherever the world is simulated: on a server, or inside your own game in single player. Players joining a server never run its scripts.

• Plain data in, a request out

  A script is handed plain values and hands back what it would like to happen. The game checks that request and applies it the same way it applies anything a player does.

• Walled off

  No files, no clock and no loading code from text. A script can only see the small set of functions the game gives it.

• On a budget

  Every call has a limit. A script that runs too long is stopped and its mod is switched off, without taking the game down with it.

• Repeatable

  Randomness comes from the world and the game clock, so the same moment in the same world always gives the same result.

• Never compiled code

  Mods are data and Lua, never compiled code. A mod can't run a program on your computer, and that isn't going to change.

What scripts might look like

-- Cloudberries keep you a little warmer.
-- Now and then, one warms you right through.
evolve.on_consume("northernfare:cloudberry", function(ctx)
  local warmth = 0.5

  -- ctx.random() is seeded from the world, so the same
  -- moment in the same world always gives the same roll.
  if ctx.random() < 0.1 then
    warmth = 3
  end

  return {
    consumeItem = true,
    warmthC = warmth,
  }
end)

evolve.on_consume("northernfare:bog_water", function(ctx)
  -- ctx is plain data: what was eaten, how many,
  -- and the game tick. There's no player object here
  -- and no way into the world.
  print(ctx.item, ctx.count, ctx.tick)

  -- This asks for far more than any drink gives.
  -- The game clamps it to a sane amount first.
  return { hydrationGain = 1000 }
end)

-- None of these exist inside a mod script.
print(os)     --> nil  no clock, no system calls
print(io)     --> nil  no files
print(load)   --> nil  no running code from text
print(debug)  --> nil

-- A loop that never ends doesn't hang the server.
-- The script runs out of budget, its mod is switched off,
-- and everyone else carries on playing.
while true do end

The function names and fields in these scripts are a sketch. They'll change once I build it for real.