function init(self)
    msg.post(".", "acquire_input_focus")
    print("Initialized")

    self.speed = 0.5
    self.jumpStrength = 3
    self.gravity = 0.75
    self.velocity = vmath.vector3()

    self.velocityLimit = {}
    self.velocityLimit.horizontal = 10
    self.velocityLimit.falling = 5
    self.velocityLimit.rising = 10

    self.acceleration = vmath.vector3()
    self.accelerationLimit = 5

    self.direction = "right"
    self.grounded = false
end

function update(self, dt)
    local position = go.get_position()
    print("Absolute value of velocity.x is " .. math.abs(self.velocity.x))
    -- Change direction based on velocity.
    if self.acceleration.x > 0 then self.direction = "right" elseif self.acceleration.x < 0 then self.direction = "left" end

    -- Only apply gravity if you're not on the ground.
    if not self.grounded then self.acceleration.y = self.acceleration.y - self.gravity end

    -- If acceleration gets too high, set it to the limit based on the direction you're facing.
    if math.abs(self.acceleration) > self.accelerationLimit then
        if self.direction == "right" then self.acceleration = self.accelerationLimit
        elseif self.direction == "left" then self.acceleration = self.accelerationLimit * -1
        end
    end --if math.abs(self.acceleration)

    -- Update velocity based on acceleration.
    self.velocity.x = self.velocity.x + self.acceleration.x
    self.velocity.y = self.velocity.y + self.acceleration.y

    -- If horizontal velocity is too high, set it to the limit.
    if math.abs(self.velocity.x) > self.velocityLimit.horizontal then
        if self.direction == "right" then self.velocity.x = self.velocityLimit.horizontal
        elseif self.direction == "left" then self.velocity.x = self.velocityLimit.horizontal * -1
        end
    end -- if math.abs(self.velocity.x)

    -- If velocity is too high while falling, set it to the limit.
    if self.velocity.y < 0 then
        if math.abs(self.velocity.y) < self.velocityLimit.falling then self.velocity.y = self.velocityLimit.falling end

    -- If velocity is too high while rising, set it to the limit. Also use this check to set not grounded while in the air.
    elseif self.velocity.y > 0 then
        self.grounded = false
        if math.abs(self.velocity.y) > self.velocityLimit.rising then self.velocity.y = self.velocityLimit.rising end
    end -- if self.velocity.y

    position.x = position.x + self.velocity.x
    position.y = position.y + self.velocity.y
    go.set_position(position)

end


function on_message(self, message_id, message, sender)
    if message_id == hash("collision_response") then
        if message.other_group == hash("Terrain") then

            -- If you collide with terrain underneath you and you're not grounded, stop vertical velocity and set grounded to true.
            -- Otherwise, if you collide with terrain above you, just stop vertical velocity.
            if message.other_position.y < go.get_position().y and not self.grounded then
                self.velocity.y = 0
                self.grounded = true
            elseif message.other_position.y > go.get_position().y then self.velocity.y = 0
            end --if message.other_position.y
        end --if message.other_group
    end -- if message_id
end

function on_input(self, action_id, action)

    if action_id == hash("left") then
        self.acceleration.x = self.acceleration.x - self.speed
        print("Left detected!")
    elseif action_id == hash("right") then
        self.acceleration.x = self.acceleration.x + self.speed
        print("Right detected!")
    elseif action_id == hash("up") then
        self.acceleration.y = self.acceleration.y + self.jumpStrength
        print("Up detected!")
    end --if action_id


end --function on_input