diff --git a/engine.lua b/engine.lua
new file mode 100644
index 0000000..f42a214
--- /dev/null
+++ b/engine.lua
@@ -0,0 +1,122 @@
+--[[
+Copyright 2025 Andrey Stepanov
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+]]--
+
+local storage = minetest.get_mod_storage()
+
+local dig_penalty_storage = {}
+if storage:contains("dig_penalty") then
+    dig_penalty_storage = minetest.deserialize(
+        storage:get_string("dig_penalty")
+    )
+end
+
+
+---@param dig_penalty number
+local function set_dig_penalty(player, dig_penalty)
+    local pname = player:get_player_name()
+    local prev_dig_penalty = dig_penalty_storage[pname] or 1
+    if dig_penalty == prev_dig_penalty then
+        return
+    end
+    dig_penalty_storage[pname] = dig_penalty
+    storage:set_string(
+        "dig_penalty",
+        minetest.serialize(
+            dig_penalty_storage
+        )
+    )
+
+    local inv = player:get_inventory()
+    local inv_size = inv:get_size("main")
+    for i = 1, inv_size do
+        local stack = inv:get_stack("main", i)
+        if not stack:is_empty() then
+            toolcap_monoids.dig_speed:del_change(stack, "medical")
+            if dig_penalty ~= 1 then
+                toolcap_monoids.dig_speed:add_change(stack, dig_penalty, "medical")
+            end
+            inv:set_stack("main", i, stack)
+        end
+    end
+
+    hand_monoid.monoid:del_change(player, "medical")
+    local hand_caps = table.copy(hand_monoid.monoid_def.identity.groupcaps)
+    if dig_penalty ~= 1 then
+        for group, cap in pairs(hand_caps) do
+            if cap.times then
+                for i, _ in pairs(cap.times) do
+                    cap.times[i] = cap.times[i] * dig_penalty
+                end
+            end
+        end
+        hand_monoid.monoid:add_change(
+            player,
+            {
+                groupcaps = hand_caps
+            },
+            "medical"
+        )
+    end
+end
+
+
+minetest.register_on_newplayer(
+    function(player)
+        hand_monoid.monoid:add_change(
+            player,
+            {
+                groupcaps = table.copy(hand_monoid.monoid_def.identity.groupcaps)
+            },
+            "medical"
+        )
+    end
+)
+
+
+minetest.register_on_player_inventory_action(
+    function(
+            player,
+            action,
+            inventory,
+            inventory_info
+    )
+        if action == "put" then
+            local stack = inventory_info.stack
+            local dig_penalty = dig_penalty_storage[player:get_player_name()] or 1
+            if dig_penalty ~= 1 then
+                toolcap_monoids.dig_speed:add_change(stack, dig_penalty, "medical")
+            end
+        elseif action == "take" then
+            local stack = inventory_info.stack
+            toolcap_monoids.dig_speed:del_change(stack, "medical")
+        elseif action == "move" then
+            if (inventory_info.to_list == "main") and (inventory_info.from_list ~= "main") then
+                local stack = inventory:get_stack("main", inventory_info.to_index)
+                toolcap_monoids.dig_speed:del_change(stack, "medical")
+                local dig_penalty = dig_penalty_storage[player:get_player_name()] or 1
+                if dig_penalty ~= 1 then
+                    toolcap_monoids.dig_speed:add_change(stack, dig_penalty, "medical")
+                end
+                inventory:set_stack("main", inventory_info.to_index, stack)
+            elseif (inventory_info.from_list == "main") and (inventory_info.to_list ~= "main") then
+                local stack = inventory:get_stack(inventory_info.to_list, inventory_info.to_index)
+                toolcap_monoids.dig_speed:del_change(stack, "medical")
+                inventory:set_stack(inventory_info.to_list, inventory_info.to_index, stack)
+            end
+        end
+    end
+)
+
diff --git a/init.lua b/init.lua
index 7b791fe..a50dbab 100644
--- a/init.lua
+++ b/init.lua
@@ -17,4 +17,5 @@ limitations under the License.
 
 medical = {}
 local MP = minetest.get_modpath("medical")
+dofile(MP .. "/engine.lua")
 dofile(MP .. "/gui.lua")
\ No newline at end of file
diff --git a/mod.conf b/mod.conf
index 4235ffa..1cadb01 100644
--- a/mod.conf
+++ b/mod.conf
@@ -1,3 +1,3 @@
 name = medical
 description = Health and nutrition
-depends = unified_inventory
\ No newline at end of file
+depends = unified_inventory, toolcap_monoids, hand_monoid
\ No newline at end of file