sdl2-space-invaders

A SDL2 implementation of the classic Space Invaders game.

This implementation supports one and two players.

Development blog entry: https://toivjon.wordpress.com/2017/10/22/sdl2-space-invaders/

Scenes

Game is split into following scenes:

1. A welcome scene, which contains the main menu and score descriptions.
2. A "play player" scene, which tells which player should prepare to play.
3. An in-game scene, which contains the actual gameplay.

The list of scene transitions:

• 1 to 2, when the number of players has been selected.
• 2 to 3, after 150 ticks.
• 3 to 2, after a level has been cleared i.e. all aliens has been destroyed.
• 3 to 2, after player has been killed and other player has still lives left (multiplayer only).
• 3 to 1, after pressing the enter key when game over text is being shown.

Features

This Space Invaders implementation contains the following features:

• A support for one or two player (turn-based) games.
• Each player has three lives.
• Each level lasts until avatar or all aliens are destroyed or if any of the aliens invades.
• Game ends after each player has lost their lives.
• Player game state is stored when toggling between players in the two player mode.
• Aliens may shoot three different kind of missiles (rolling, plunger and squiggly).
• Plunger and squiggly alien shots follow predefined shoot patterns.
• Rolling shot is always launched from the players nearest alien.
• Game field contains four pixelwise destructable shields.
• Players earn points based on the destructed alien type.
• Alien movement speed is increased after the number of shown aliens decreases.
• Alien missile fire rate depends on the player score.
• Alien starting y-position depends on the level number.
• Flying saucer will be shown about periodically after each ~1200 ticks.
• Points received from the flying saucer is based on a lookup-table and player shot count.

External Dependencies

This implementation has external dependencies on the following libraries:

• SDL2
• SDL2_ttf
• SDL2_image
• libfreetype-6.dll
• zlib1.dll
• libpng16-16.dll

Compilation

Easiest way to compile the code is to use the CMake utility.

Required tools and libraries for the compilation:

1. CMake (ver. >=3.7.2)
2. SDL2 (ver. >=2.0.5)
3. SDL2_ttf (ver. >=2.0.14)
4. SDL2_image (ver. >= 2.0.2)
5. A compilation toolkit supported by the CMake utility (e.g. Visual Studio).

CMake compilation uses Find*-modules from the /cmake folder which specify where CMake looks for the required libraries.

Without any modifications, CMake will make use the following environment variable paths.

• SDL2DIR, which should point to the root directory of the SDL2 library.
• SDL2TTFDIR, which should point to the root directory of the SDL2_ttf library.
• SDL2IMAGEDIR, which should point to the root directory of the SDL2_image library.

Screenshots