Move at the speed of time

Movement connects input, math, and the game loop. We want the player to travel at a speed measured in pixels per second, regardless of the computer’s frame rate.

See why dt matters

Suppose you add four pixels every frame:

player.x = player.x + 4

At 30 frames per second that travels 120 pixels in one second. At 120 FPS it travels 480. The faster computer changes the game.

Use a speed and elapsed time instead:

player.x = player.x + player.speed * dt

If speed is 240 pixels per second, the one-second distance stays 240.

Poll held keys

Movement should continue as long as a key is held. Poll the current keyboard state during every update:

if love.keyboard.isDown("right", "d") then
  player.x = player.x + player.speed * dt
end

isDown can accept more than one key and returns true if any is held. Later, love.keypressed will handle one-time actions such as starting a game.

Add speed to the player table:

local player = {
  x = 480,
  y = 360,
  radius = 14,
  speed = 260,
}

Then replace love.update with this first movement version, keeping the signal pulse line:

function love.update(dt)
  signal.pulse = signal.pulse + dt * 4

  if love.keyboard.isDown("left", "a") then
    player.x = player.x - player.speed * dt
  end
  if love.keyboard.isDown("right", "d") then
    player.x = player.x + player.speed * dt
  end
  if love.keyboard.isDown("up", "w") then
    player.y = player.y - player.speed * dt
  end
  if love.keyboard.isDown("down", "s") then
    player.y = player.y + player.speed * dt
  end
end

Run the game and move with WASD or the arrows.

Fix faster diagonal movement

The code above adds full horizontal and vertical movement simultaneously. If both components are 260, diagonal speed is about 368 because of the Pythagorean theorem:

√(260² + 260²) ≈ 368

Build a direction first, then normalize it to length 1:

local dx, dy = 0, 0

if love.keyboard.isDown("left", "a") then dx = dx - 1 end
if love.keyboard.isDown("right", "d") then dx = dx + 1 end
if love.keyboard.isDown("up", "w") then dy = dy - 1 end
if love.keyboard.isDown("down", "s") then dy = dy + 1 end

local length = math.sqrt(dx * dx + dy * dy)
if length > 0 then
  dx = dx / length
  dy = dy / length
end

player.x = player.x + dx * player.speed * dt
player.y = player.y + dy * player.speed * dt

The length > 0 guard matters. Dividing the zero vector by zero would produce invalid values.

Put that block inside love.update, after the signal update. Opposite keys cancel naturally: left contributes -1, right contributes +1, and the result is zero.

Keep the whole player on-screen

Clamping forces a value into a range:

local function clamp(value, minimum, maximum)
  return math.max(minimum, math.min(maximum, value))
end

Use the player’s radius as the margin so its edge—not only its center—stays visible:

player.x = clamp(
  player.x + dx * player.speed * dt,
  player.radius,
  love.graphics.getWidth() - player.radius
)

player.y = clamp(
  player.y + dy * player.speed * dt,
  player.radius,
  love.graphics.getHeight() - player.radius
)

This replaces the two simple position assignments. Try holding two direction keys into each corner.

Continuous state versus discrete events

Use the right kind of input for the action:

If you start a game by polling Enter, the key may still be held on the next frame and trigger something again. Event callbacks represent the edge: the moment a key becomes down.

local currentSpeed = player.speed
if love.keyboard.isDown("lshift", "rshift") then
  currentSpeed = currentSpeed * 1.6
end