LÖVE

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Error:
main.lua:39: Need at least three vertices to draw a polygon.

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-- light source (point) in world coordinates
local wox, woy = 0, 0
-- cast distance
local cast = 500

local si, ei = 1, #polygon
-- get the last vertex (A) of the polygon
local ls = polygon[ei]
-- (optional) if the vertex is in local coords, transform to world coords
local wax, way = get_world_point(enemy.x, enemy.y, ls.x, ls.y)
-- cast a line from vertex A (wax, way) away from the source (wox, woy)
local wpax, wpay = extend(wox, woy, wax, way, cast)

-- for each edge in the polygon
for i = si, ei do
  -- get the "next" vertex (B)
  local le = vertices[i]
  -- (optional) transform vertex B to world coords
  local wbx, wby = get_world_point(enemy.x, enemy.y, le.x, le.y)
  -- cast a line from vertex B (wax, way) away from the source (wox, woy)
  local wpbx, wpby = extend(wox, woy, wbx, wby, cast)

  -- (optional) don't cast front shadows
  local dx, dy = wox - wbx, woy - wby
  local hx, hy = wbx - wax, wby - way
  hx, hy = -hy, hx
  local dot = dx*hx + dy*hy
  -- don't draw if it's a front shadow
  if dot > 0 then
    -- draw a polygon:
    -- wax, way (vertex A)
    -- wpax, wpay (extended vertex A)
    -- wpbx, wpby (extended vertex B)
    -- wbx, wby (vertex B)
  end
  -- make vertex B the "last" vertex
  wax, way = wbx, wby
  wpax, wpay = wpbx, wpby
end

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-- Moves one point (x2, y2) away from another (x, y) by the given distance (dist)
local extend = function(x, y, x2, y2, dist)
  local dx, dy = x2 - x, y2 - y
  local d = math.sqrt(dx*dx + dy*dy)
  d = 1/d*dist
  return dx*d + x, dy*d + y
end
-- Transforms local point lx, ly to world coordinates
local get_world_point = function(x, y, lx, ly)
  -- translation only (optional: add rotation and scale)
  return lx + x, ly + y
end

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enemy =
{
  -- position
  x = 0, y = 0,
  -- local vertices: top left, top right, bottom right, bottom left
  vertices = { { x = 0, y = 0 }, { x = w, y = 0 }, { x = w, y = h }, { x = 0, y = h } }
}

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local Handler = {};

-- ------------------------------------------------
-- Public Functions
-- ------------------------------------------------

function Handler.save(profile)
    local file = love.filesystem.newFile('player.sav', 'w');

    file:write('return {\n');
    for key, value in pairs(profile) do
        file:write(string.format('    %s = %s,\n', key, tostring(value)));
    end
    file:write('};');
end

function Handler.load()
    local file = love.filesystem.load('player.sav');

    if file then
        return file();
    end
end

function Handler.delete()
    return love.filesystem.remove('player.sav');
end

return Handler;