diff --git a/.gitignore b/.gitignore
index 3313fb28c..03c1e0571 100644
--- a/.gitignore
+++ b/.gitignore
@@ -19,6 +19,7 @@ emu
 koreader-*.zip
 koreader-*.apk
 koreader-*.tar.gz
+koreader-*.targz
 koreader-*.click
 
 l10n/*
diff --git a/frontend/apps/reader/modules/readerscreenshot.lua b/frontend/apps/reader/modules/readerscreenshot.lua
index b7284a285..0149c7c64 100644
--- a/frontend/apps/reader/modules/readerscreenshot.lua
+++ b/frontend/apps/reader/modules/readerscreenshot.lua
@@ -42,7 +42,7 @@ function ReaderScreenshot:onScreenshot(filename)
     local screenshot_name = filename or os.date(self.datetime_name)
     UIManager:show(InfoMessage:new{
         text = T( _("Saving screenshot to %1."), screenshot_name),
-        timeout = 2,
+        timeout = 3,
     })
     Screen:shot(screenshot_name)
     -- trigger full refresh
diff --git a/frontend/ui/message/filemessagequeue.lua b/frontend/ui/message/filemessagequeue.lua
index eb88e2874..a7ae45ee1 100644
--- a/frontend/ui/message/filemessagequeue.lua
+++ b/frontend/ui/message/filemessagequeue.lua
@@ -1,9 +1,6 @@
 local ffi = require("ffi")
 local DEBUG = require("dbg")
-local util = require("ffi/util")
-local Event = require("ui/event")
 local MessageQueue = require("ui/message/messagequeue")
-
 local dummy = require("ffi/zeromq_h")
 local czmq = ffi.load("libs/libczmq.so.1")
 local filemq = ffi.load("libs/libfmq.so.1")
diff --git a/frontend/ui/widget/infomessage.lua b/frontend/ui/widget/infomessage.lua
index 6cfa628fc..2b8f5a78f 100644
--- a/frontend/ui/widget/infomessage.lua
+++ b/frontend/ui/widget/infomessage.lua
@@ -46,7 +46,7 @@ function InfoMessage:init()
             }
         }
     end
-    local image_widget = nil
+    local image_widget
     if self.image then
         image_widget = ImageWidget:new{
             image = self.image,
diff --git a/frontend/ui/widget/inputtext.lua b/frontend/ui/widget/inputtext.lua
index 6c8981abf..bc01827a7 100644
--- a/frontend/ui/widget/inputtext.lua
+++ b/frontend/ui/widget/inputtext.lua
@@ -5,11 +5,9 @@ local FrameContainer = require("ui/widget/container/framecontainer")
 local VirtualKeyboard = require("ui/widget/virtualkeyboard")
 local GestureRange = require("ui/gesturerange")
 local UIManager = require("ui/uimanager")
-local Geom = require("ui/geometry")
 local Device = require("device")
 local Screen = require("device").screen
 local Font = require("ui/font")
-local DEBUG = require("dbg")
 local util = require("ffi/util")
 local Blitbuffer = require("ffi/blitbuffer")
 
@@ -54,7 +52,6 @@ function InputText:initTextBox(text)
     self:initCharlist(text)
     local fgcolor = Blitbuffer.gray(self.text == "" and 0.5 or 1.0)
 
-    local text_widget = nil
     local show_text = self.text
     if self.text_type == "password" and show_text ~= "" then
         show_text = self.text:gsub("(.-).", function() return "*" end)
@@ -62,6 +59,7 @@ function InputText:initTextBox(text)
     elseif show_text == "" then
         show_text = self.hint
     end
+    local text_widget
     if self.scroll then
         text_widget = ScrollTextWidget:new{
             text = show_text,
diff --git a/frontend/ui/widget/logindialog.lua b/frontend/ui/widget/logindialog.lua
index db1b84551..371cba5cc 100644
--- a/frontend/ui/widget/logindialog.lua
+++ b/frontend/ui/widget/logindialog.lua
@@ -6,7 +6,6 @@ local InputText = require("ui/widget/inputtext")
 local UIManager = require("ui/uimanager")
 local Geom = require("ui/geometry")
 local Screen = require("device").screen
-local DEBUG = require("dbg")
 local _ = require("gettext")
 local Blitbuffer = require("ffi/blitbuffer")
 
diff --git a/frontend/ui/widget/menu.lua b/frontend/ui/widget/menu.lua
index ea9fc87d2..6ce03f4be 100644
--- a/frontend/ui/widget/menu.lua
+++ b/frontend/ui/widget/menu.lua
@@ -6,7 +6,6 @@ local FrameContainer = require("ui/widget/container/framecontainer")
 local CenterContainer = require("ui/widget/container/centercontainer")
 local BottomContainer = require("ui/widget/container/bottomcontainer")
 local UnderlineContainer = require("ui/widget/container/underlinecontainer")
-local HorizontalSpan = require("ui/widget/horizontalspan")
 local FocusManager = require("ui/widget/focusmanager")
 local TextWidget = require("ui/widget/textwidget")
 local OverlapGroup = require("ui/widget/overlapgroup")
@@ -54,7 +53,7 @@ function ItemShortCutIcon:init()
     end
 
     --@TODO calculate font size by icon size  01.05 2012 (houqp)
-    local sc_face = nil
+    local sc_face
     if self.key:len() > 1 then
         sc_face = Font:getFace("ffont", 14)
     else
@@ -167,7 +166,7 @@ function MenuItem:init()
 
     local state_button_width = self.state_size.w or 0
     local my_text = self.text and ""..self.text or ""
-    w = RenderText:sizeUtf8Text(0, self.dimen.w, self.face,
+    local w = RenderText:sizeUtf8Text(0, self.dimen.w, self.face,
                     ""..my_text, true, self.bold).x
     if w + mandatory_w + state_button_width >= self.content_width then
         if Device:hasKeyboard() then
@@ -245,7 +244,6 @@ function MenuItem:init()
             ItemShortCutIcon:new{
                 dimen = shortcut_icon_dimen,
                 key = self.shortcut,
-                radius = shortcut_icon_r,
                 style = self.shortcut_style,
             },
             HorizontalSpan:new{ width = 10 },
@@ -501,7 +499,7 @@ function Menu:init()
         }
     }
 
-    local content = nil
+    local content
     if self.no_title then
         content = OverlapGroup:new{
             dimen = self.dimen:copy(),
@@ -855,7 +853,7 @@ function Menu:onClose()
         self:onCloseAllMenus()
     else
         -- back to parent menu
-        parent_item_table = table.remove(self.item_table_stack, table_length)
+        local parent_item_table = table.remove(self.item_table_stack, table_length)
         self:swithItemTable(parent_item_table.title, parent_item_table)
     end
     return true
diff --git a/frontend/ui/widget/multiconfirmbox.lua b/frontend/ui/widget/multiconfirmbox.lua
index 259c402ac..4a4e53665 100644
--- a/frontend/ui/widget/multiconfirmbox.lua
+++ b/frontend/ui/widget/multiconfirmbox.lua
@@ -7,11 +7,7 @@ local ImageWidget = require("ui/widget/imagewidget")
 local TextBoxWidget = require("ui/widget/textboxwidget")
 local HorizontalSpan = require("ui/widget/horizontalspan")
 local ButtonTable = require("ui/widget/buttontable")
-local GestureRange = require("ui/gesturerange")
 local UIManager = require("ui/uimanager")
-local Device = require("device")
-local Geom = require("ui/geometry")
-local Input = require("device").input
 local Screen = require("device").screen
 local Font = require("ui/font")
 local DEBUG = require("dbg")
diff --git a/frontend/ui/widget/multiinputdialog.lua b/frontend/ui/widget/multiinputdialog.lua
index c319f8a3f..b8c1069d3 100644
--- a/frontend/ui/widget/multiinputdialog.lua
+++ b/frontend/ui/widget/multiinputdialog.lua
@@ -1,18 +1,14 @@
 local FrameContainer = require("ui/widget/container/framecontainer")
 local CenterContainer = require("ui/widget/container/centercontainer")
 local VerticalGroup = require("ui/widget/verticalgroup")
-local HorizontalGroup = require("ui/widget/horizontalgroup")
 local InputDialog = require("ui/widget/inputdialog")
 local InputText = require("ui/widget/inputtext")
 local UIManager = require("ui/uimanager")
 local Geom = require("ui/geometry")
 local Screen = require("device").screen
-local DEBUG = require("dbg")
 local _ = require("gettext")
-local util = require("ffi/util")
 local Blitbuffer = require("ffi/blitbuffer")
 
-local InfoMessage = require("ui/widget/infomessage")
 local input_field
 
 local MultiInputDialog = InputDialog:extend{
diff --git a/frontend/ui/widget/notification.lua b/frontend/ui/widget/notification.lua
index d8db5dbed..8986c8c4a 100644
--- a/frontend/ui/widget/notification.lua
+++ b/frontend/ui/widget/notification.lua
@@ -6,7 +6,6 @@ local Font = require("ui/font")
 local Geom = require("ui/geometry")
 local Device = require("device")
 local UIManager = require("ui/uimanager")
-local HorizontalGroup = require("ui/widget/horizontalgroup")
 local Input = require("device").input
 local Screen = require("device").screen
 local Blitbuffer = require("ffi/blitbuffer")
diff --git a/frontend/ui/widget/opdsbrowser.lua b/frontend/ui/widget/opdsbrowser.lua
index 5ec20f43a..0d77f0be1 100644
--- a/frontend/ui/widget/opdsbrowser.lua
+++ b/frontend/ui/widget/opdsbrowser.lua
@@ -2,20 +2,17 @@ local MultiInputDialog = require("ui/widget/multiinputdialog")
 local ButtonDialog = require("ui/widget/buttondialog")
 local InfoMessage = require("ui/widget/infomessage")
 local LoginDialog = require("ui/widget/logindialog")
-local lfs = require("libs/libkoreader-lfs")
 local OPDSParser = require("ui/opdsparser")
 local NetworkMgr = require("ui/networkmgr")
 local UIManager = require("ui/uimanager")
 local CacheItem = require("cacheitem")
 local Menu = require("ui/widget/menu")
 local Screen = require("device").screen
-local Device = require("device")
 local url = require('socket.url')
 local util = require("ffi/util")
 local Cache = require("cache")
 local DEBUG = require("dbg")
 local _ = require("gettext")
-local ffi = require("ffi")
 
 local socket = require('socket')
 local http = require('socket.http')
@@ -189,7 +186,6 @@ function OPDSBrowser:genItemTableFromRoot()
         })
     end
     local calibre_opds = G_reader_settings:readSetting("calibre_opds") or {}
-    local calibre_callback = nil
     if not calibre_opds.host or not calibre_opds.port then
         table.insert(item_table, {
             text = self.calibre_name,
@@ -241,7 +237,7 @@ function OPDSBrowser:getAuthorizationHeader(host)
 end
 
 function OPDSBrowser:fetchFeed(feed_url)
-    local headers, request, sink = {}, {}, {}
+    local request, sink = {}, {}
     local parsed = url.parse(feed_url)
     request['url'] = feed_url
     request['method'] = 'GET'
@@ -324,7 +320,7 @@ function OPDSBrowser:getCredential()
 end
 
 function OPDSBrowser:parseFeed(feed_url)
-    local feed = nil
+    local feed
     local hash = "opds|catalog|" .. feed_url
     local cache = CatalogCache:check(hash)
     if cache then
@@ -333,10 +329,7 @@ function OPDSBrowser:parseFeed(feed_url)
         DEBUG("cache", hash)
         feed = self:fetchFeed(feed_url)
         if feed then
-            local cache = CatalogCacheItem:new{
-                feed = feed
-            }
-            CatalogCache:insert(hash, cache)
+            CatalogCache:insert(hash, CatalogCacheItem:new{ feed = feed })
         end
     end
     if feed then
@@ -417,7 +410,6 @@ function OPDSBrowser:genItemTableFromCatalog(catalog, item_url)
                     end
                 end
                 local title = "Unknown"
-                local title_type = type(entry.title)
                 if type(entry.title) == "string" then
                     title = entry.title
                 elseif type(entry.title) == "table" then
@@ -445,8 +437,8 @@ function OPDSBrowser:genItemTableFromCatalog(catalog, item_url)
     return item_table
 end
 
-function OPDSBrowser:updateCatalog(url)
-    local menu_table = self:genItemTableFromURL(url)
+function OPDSBrowser:updateCatalog(item_table_url)
+    local menu_table = self:genItemTableFromURL(item_table_url)
     if #menu_table > 0 then
         --DEBUG("menu table", menu_table)
         self:swithItemTable(nil, menu_table)
@@ -457,8 +449,8 @@ function OPDSBrowser:updateCatalog(url)
     end
 end
 
-function OPDSBrowser:appendCatalog(url)
-    local new_table = self:genItemTableFromURL(url)
+function OPDSBrowser:appendCatalog(item_table_url)
+    local new_table = self:genItemTableFromURL(item_table_url)
     for i, item in ipairs(new_table) do
         table.insert(self.item_table, item)
     end
diff --git a/frontend/ui/widget/pathchooser.lua b/frontend/ui/widget/pathchooser.lua
index 2987b0efb..6f7694486 100644
--- a/frontend/ui/widget/pathchooser.lua
+++ b/frontend/ui/widget/pathchooser.lua
@@ -2,7 +2,6 @@ local ButtonDialog = require("ui/widget/buttondialog")
 local FileChooser = require("ui/widget/filechooser")
 local UIManager = require("ui/uimanager")
 local util = require("ffi/util")
-local DEBUG = require("dbg")
 local _ = require("gettext")
 
 local PathChooser = FileChooser:extend{
diff --git a/frontend/ui/widget/textboxwidget.lua b/frontend/ui/widget/textboxwidget.lua
index 01e25153d..853118d65 100644
--- a/frontend/ui/widget/textboxwidget.lua
+++ b/frontend/ui/widget/textboxwidget.lua
@@ -1,10 +1,6 @@
-local InputContainer = require("ui/widget/container/inputcontainer")
 local Blitbuffer = require("ffi/blitbuffer")
 local Widget = require("ui/widget/widget")
-local GestureRange = require("ui/gesturerange")
 local RenderText = require("ui/rendertext")
-local UIManager = require("ui/uimanager")
-local Device = require("device")
 local Screen = require("device").screen
 local Geom = require("ui/geometry")
 local util = require("util")
@@ -29,7 +25,7 @@ local TextBoxWidget = Widget:new{
 }
 
 function TextBoxWidget:init()
-    local v_list = nil
+    local v_list
     if self.height then
         v_list = self:_getCurrentVerticalList()
     else
@@ -81,7 +77,6 @@ function TextBoxWidget:_getVerticalList(alg)
     end
     -- build horizontal list
     local h_list = {}
-    local line_count = 0
     for line in util.gsplit(self.text, "\n", true) do
         for words in line:gmatch("[\32-\127\192-\255]+[\128-\191]*") do
             for word in util.gsplit(words, "%s+", true) do
@@ -179,12 +174,11 @@ function TextBoxWidget:_render(v_list)
     self.rendering_vlist = v_list
     local font_height = self.face.size
     local line_height_px = self.line_height * font_height
-    local space_w = RenderText:sizeUtf8Text(0, Screen:getWidth(), self.face, " ", true).x
     local h = (font_height + line_height_px) * #v_list
     self._bb = Blitbuffer.new(self.width, h)
     self._bb:fill(Blitbuffer.COLOR_WHITE)
     local y = font_height
-    local pen_x = 0
+    local pen_x
     for _,l in ipairs(v_list) do
         pen_x = 0
         for _,w in ipairs(l) do
diff --git a/frontend/ui/widget/toggleswitch.lua b/frontend/ui/widget/toggleswitch.lua
index a573e4748..8d6dcad4b 100644
--- a/frontend/ui/widget/toggleswitch.lua
+++ b/frontend/ui/widget/toggleswitch.lua
@@ -10,7 +10,6 @@ local UIManager = require("ui/uimanager")
 local Screen = require("device").screen
 local Device = require("device")
 local GestureRange = require("ui/gesturerange")
-local DEBUG = require("dbg")
 local Blitbuffer = require("ffi/blitbuffer")
 local _ = require("gettext")
 
@@ -130,7 +129,6 @@ function ToggleSwitch:onTapSelect(arg, gev)
     local position = math.ceil(
         (gev.pos.x - self.dimen.x) / self.dimen.w * self.n_pos
     )
-    --DEBUG("toggle position:", position)
     self:togglePosition(position)
     --[[
     if self.values then
diff --git a/frontend/ui/widget/touchmenu.lua b/frontend/ui/widget/touchmenu.lua
index a23cd44e5..a95f5a096 100644
--- a/frontend/ui/widget/touchmenu.lua
+++ b/frontend/ui/widget/touchmenu.lua
@@ -18,7 +18,6 @@ local Screen = require("device").screen
 local Geom = require("ui/geometry")
 local Font = require("ui/font")
 local util = require("ffi/util")
-local DEBUG = require("dbg")
 local _ = require("gettext")
 local Blitbuffer = require("ffi/blitbuffer")
 
diff --git a/frontend/util.lua b/frontend/util.lua
index 470976640..4c9d0c940 100644
--- a/frontend/util.lua
+++ b/frontend/util.lua
@@ -47,8 +47,8 @@ function util.gsplit(str, pattern, capture)
 end
 
 --https://gist.github.com/jesseadams/791673
-function util.secondsToClock(seconds, withoutSeconds)
-    local seconds = tonumber(seconds)
+function util.secondsToClock(sec, withoutSeconds)
+    local seconds = tonumber(sec)
     if seconds == 0 or seconds ~= seconds then
         if withoutSeconds then
             return "00:00";