local function load_highscore()
    local filename = sys.get_save_file("sys_save_load", "highscore") -- <1>
    local data = sys.load(filename) -- <2>
    return data.highscore or 0  -- <3>
end

local function save_highscore(highscore)
    local filename = sys.get_save_file("sys_save_load", "highscore")
    sys.save(filename, { highscore = highscore })  -- <4>
end

local function update_labels(score, highscore)
    label.set_text("score#score", tostring(score))
    label.set_text("score#highscore", "HIGH SCORE\n" .. tostring(highscore))
end

function init(self)
    msg.post(".", "acquire_input_focus")
    self.score = 0
    self.highscore = load_highscore()
    update_labels(self.score, self.highscore)
end

function update(self, dt)
    if self.pressed then
        self.score = self.score + math.ceil(100 * dt)
        update_labels(self.score, self.highscore)
    end
end

function on_input(self, action_id, action)
    if action_id == hash("touch") then
        if action.pressed then
            self.score = 0
            self.pressed = true
        elseif action.released then
            self.pressed = false
            if self.score > self.highscore then
                self.highscore = self.score
                save_highscore(self.highscore)
                update_labels(self.score, self.highscore)
            end
        end
    end
end

--[[
1. Get an application specific path for the file "highscore"
2. Load saved data.
3. The returned data is a Lua table with the saved values or an empty table if nothing has been saved.
4. Save data. The data to save must be stored in a Lua table.
--]]