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Shoot bullets


Setup

This example shows how to dynamically spawn bullet game objects using a factory component and how to also move and delete the bullets. The setup consists of two game objects; one for the player and one for the bullet that is spawned using a factory component.

Combine this example with some of the examples from the movement and physics categories to create a shoot ‘em up game!

player
The red ship at the bottom. Contains:
  • A Sprite component with the spaceship image.
  • A Factory component to spawn bullet game objects
  • A script to handle spawning of bullets.
bullet
The bullet fired by the player. Contains:
  • A Sprite component with a bullet image.

Scripts

player.script

function init(self)
    -- make sure the script will receive user input
    msg.post(".", "acquire_input_focus")
end

function on_input(self, action_id, action)
    -- mouse or spacebar
    if (action_id == hash("touch") or action_id == hash("action")) and action.pressed then
        -- position bullet somewhat offset from the player position
        local pos = go.get_position()
        pos.y = pos.y + 50

        -- spawn a bullet
        local bullet_id = factory.create("#bulletfactory", pos)

        -- animate the bullet
        local distance = 1000                   -- distance in pixels
        local speed = 800                       -- pixels per second
        local duration = distance / speed       -- time in second to travel the full distance
        local to = pos.y + distance
        -- start animation and delete bullet when it has reached its destination
        go.animate(bullet_id, "position.y", go.PLAYBACK_ONCE_FORWARD, to, go.EASING_LINEAR, duration, 0, function()
            go.delete(bullet_id)
        end)
    end
end

If you want to play with these examples, you can get the project on Github.

Do you want to see more examples? Why not write a few yourself and submit a pull request? We love contributions.

GITHUB