Having an issue with grid-based movement in Love2D/Lua - lua

Question

Using the Love2D Lua framework, I am trying to program a very basic game much like Nintendo-era RPGs where the heroes' and NPCs' movement was restricted to a tiled grid. So far I've found my past any problems, until I hit this tricky error where the player movement isn't functioning correctly.
function love.load()
love.graphics.setDefaultFilter('nearest', 'nearest', 1)
love.keyboard.setKeyRepeat(true)
font = love.graphics.newFont(14) -- the number denotes the font size
win_size = 6
love.window.setMode(160 * win_size, 144 * win_size)
true_sfc = love.graphics.newCanvas(160,144)
view_sfc = love.graphics.newCanvas(160 * win_size, 144 * win_size)
player = {
grid_x = 3,
grid_y = 3,
act_x = 48,
act_y = 48,
transit = false,
direction = {0, 0}
}
end
function love.update(dt)
if player.transit == true then
-- The idea is that if the player selects a direction, the player will walk in that direction until it stops on the grid.
-- When I press left or right, the movements works as intended- the player square walks until it stops on the grid.
-- However, when I press up or down, the player only moves a single pixel, despite having the same instructions
player.act_x = player.act_x + player.direction[1]
player.act_y = player.act_y + player.direction[2]
if player.act_x == player.grid_x * 16 then
player.direction[1] = 0
player.transit = false
end
if player.act_y == player.grid_y * 16 then
player.direction[2] = 0
player.transit = false
end
-- Now in this if-statement, if I have the program compare the player's y-coordinates before comparing the x coordinates,
-- the program will move the player on the y-axis correctly, with it locking to the 16 pixel grid, while the x coordinates
-- will starts to have the single-pixel movement issue.
end
end
function love.draw()
love.graphics.setCanvas(true_sfc)
love.graphics.setColor( 0, 0, 0)
love.graphics.rectangle("fill", 0, 0, 256, 224)
love.graphics.setColor(255,255,255)
love.graphics.rectangle("fill", player.act_x, player.act_y, 16, 16)
love.graphics.print(player.direction[1], 100, 100)
love.graphics.print(player.direction[2], 100, 120)
love.graphics.setCanvas()
love.graphics.draw(true_sfc, 0, 0, 0, win_size, win_size)
end
function love.keypressed(key)
if player.transit == false then
if key == "up" then
player.grid_y = player.grid_y - 1
player.direction = {0, -1}
player.transit = true
elseif key == "down" then
player.grid_y = player.grid_y + 1
-- press down, the player's map position goes down one tile
player.direction = {0, 1}
player.transit = true
elseif key == "left" then
player.grid_x = player.grid_x - 1
player.direction = {-1, 0}
player.transit = true
elseif key == "right" then
player.grid_x = player.grid_x + 1
player.direction = {1, 0}
player.transit = true
end
end
end
Admittedly I'm pretty new to Lua so I don't understand how it uses variables very well. And I realize that my code isn't very effecient, but that's something I planned on improving over time anyway.

Answer 1

The problem here is that you check if the vertical movement lines up, see that it does, and then you set self.transit to false, preventing any future checks.
You want to also check that you are moving in that direction, before checking if you're lined up:
if player.direction[1] ~= 0 and player.act_x == player.grid_x * 16 then
player.direction[1] = 0
player.transit = false
end
if player.direction[2] ~= 0 and player.act_y == player.grid_y * 16 then
player.direction[2] = 0
player.transit = false
end