• Ultra-versatile: game states, AI, etc.
• Easy to implement (switch/polymorphism)

• Ideally render frames 60 times per second (60 fps)
• Two steps each frame: update and render

• Each state represents a "screen" in the game (the main menu, a level…)
• They might be in a stack (for "modal" states) or in a FSM

• States might have a FSM in the inside to handle the different stages

• Images with movement/behaviour
• They can intereact between them (i.e. a bullet destroying an enemy alien)
• They can be animated

• frame-by-frame: a different picture is used for every part of the animation
• There is no interpolation
• Usually stored in spritesheets for performance

• "South Park"-like
• A sprite is decomposed into parts that are rotated, moved, etc.
• There is interpolation
• More smooth… but may look odd if not combined with keyframes

• Entities: sprites, UI elements, particle systems, texts, etc.
• They can be organised in a tree structure that represents the game world
• If a tree, hierarchical relationships can be useful for handling entities relatively to a parent

See Metal vs Hipsters

• It's useful to group similar sprites in lists (f.ex: to check collisions between all the lasers and all the enemies)
• Pools can be considered (or not) entities.

• The problem: performance issues when creating and releasing sprites
• Solution: don't release sprites, mark them as "zombies" and re-use them

• Classical mechanics equations
• Relatively fast and easy to implement
• Need the delta time

• Very powerful and with interesting features
• Support for solid bodies, joints, ropes, etc.
• They map game entities to physical bodies
• Easy to use, but hard to fine-tune

• On a 2D graphic environment
• Precise… at the expense of performance

• Wrap the sprites in rects or circles and check for intersections
• The fastest method
• Trivial to implement
• Variants to support rotations: OBB, AABB

• Separating Axis Theorem
• Most physics engines use this method
• Convex polygons only!

• Your level can be bigger than the screen
• Parallax effect (layers moving at different speed)
• Camera to follow a character

• Map your world/level into a logical grid
• Grids are usually square, but can be rects, hexagons…
• Easy to perform checks and implement the game logic

• Build up your world's graphics from tiny pieces (tiles)
• Widely used in classic games
• Can be easily mapped into a logical grid

• Why? Performance
• The trick: orthogonal perspective
• Graphics are rendered as textures into quads

• Very cool to create effects: explosions, smoke, halos, etc.
• Can be as tiny as 1 pixel… (in classic games)
• …or made up of tiny polygons (3D games)

• Store the characters of a font in a spritesheet
• Easy to implement if monospaced