fix monoid

init.lua

@@ -5,15 +5,37 @@ local function bound(min, v, max)
 end
 
 more_monoids.sunlight_monoid = player_monoids.make_monoid({
+    -- additive monoid, values between -1 and 1, cuts off if sum goes beyond those
     combine = function(sunlight1, sunlight2)
-        return math.max(sunlight1, sunlight2)
+        if not sunlight1 then
+            return sunlight2
+        elseif not sunlight2 then
+            return sunlight1
+        else
+            return sunlight1 + sunlight2
+        end
     end,
     fold = function(t)
-        return #t == 0 and 0 or math.max(unpack(t))
+        local size = 0
+        local sum = 0
+        for _, v in pairs(t) do
+            if v then
+                sum = sum + v
+                size = size + 1
+            end
+        end
+        if size == 0 then
+            return nil
+        else
+            return sum
+        end
     end,
-    identity = 0,
+    identity = nil,
     apply = function(sunlight, player)
-        player:override_day_night_ratio(bound(0, sunlight, 1))
+        if sunlight then
+            sunlight = bound(0, (sunlight + 1) / 2, 1)
+        end
+        player:override_day_night_ratio(sunlight)
     end,
     on_change = function() return end,
 })