Landers | Step-by-step tutorial

Reminiscent of the classic arcade shooter space invaders, aliens from outer space have arrived in a swarm and are about to land. Can you stop wave after wave of their onslaught?

This tutorial assumes you already have a knowledge of the components of building games in Defold including input bindings, game objects, scripts, animation sets and factories. If not, you should attempt the Incoming tutorial first.

• Stage 1: importing the graphics and setting up the animation groups.
• Stage 2: moving the player's ship:
  • 2a: input bindings;
  • 2b: creating the game object;
  • 2c: writing the script to move the player ship;
• Stage 3: spawning the invaders as a swarm:
  • 3a: creating an invader game object;
  • 3b: creating a swarm game object and spawning factory;
  • 3c: writing the script to spawn the invaders;
• Stage 4: moving the invaders.
• Stage 5: firing at the invaders.
• Stage 6: destroying invaders and using particle effects:
  • 6a: creating an explosion effect;
  • 6b: setting up the collision objects;
  • 6c: writing the script to destroy the invader and play the explosion.
• Stage 7: adding some 'snap'.
• Stage 8: adding some 'crackle'.
• Stage 9: adding some 'pop'.

What you learned in this tutorial

1. Calculating hash integers from strings once instead of each time they are needed will give you a small performance boost. Algorithms can be computationally expensive, even those with an O(1) time complexity. Any unnecessary code execution should be avoided.
2. Lua does not have classic array or list data structures. Instead it uses hash tables, also known as dictionaries or associative arrays. Tables can be indexed with numbers or strings making use of efficient hashing algorithms to find data in the structure.
3. References to game objects can be added to a table enabling iteration over many game objects in a script. This is useful when you want game objects to behave both independently and as a group.
4. ParticleFX components can be attached to game objects and allow you to create simple particle effects such as explosions, smoke and blood splatters without the need for additional scripts and game objects for the individual particles.