An educational retro game using only Python? Challenge Accepted!

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@siloraptor [email protected] https://github.com/rosarior http://robertorosario.com An educational retro game using only Python? Challenge Accepted!

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Who am I?

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Who am I?

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Who am I?

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Who am I?

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Who am I? http://pythonlatino.com

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Who am I? http://pythonlatino.com

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Preamble

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Original Problem

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Problem

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Problem http://elitedaily.com

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Problem http://elitedaily.com

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Problem

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Problem

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Problem

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Problem

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Problem

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Problem

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Doing bad in school in not such a big deal

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Problem

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Problem

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Problem

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Problem

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Problem

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Problem

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Problem

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Instant action, storylines are boring

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Problem

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The eye candy, pixel wars

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And then...

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Experiment

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Experiment

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Success!

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One simple truth

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“Content is king”

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“A video game is just modern day storytelling, pixel perfect graphics, pitch perfect music are not requirements for that. Tell a story someone will want to spend time experiencing.”

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Easiest part?

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Hardest part?

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Basic Game Elements

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#1 Title screen #2 Introduction / Storyline #3 Progressive stages #4 Player #5 Bosses #6 Game over #7 Game win

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#1 Title screen - Setting (static) #2 Introduction / Storyline - Setting (scripted) #3 Progressive stages - Setting (interactive) #4 Player - Entity (controllable) #5 Bosses - Entity (autonomous) #6 Game over - Setting (scripted) #7 Game win - Setting (scripted)

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#1 Title screen - Setting (static) #2 Introduction / Storyline - Setting (scripted) #3 Progressive stages - Setting (interactive) #6 Game over - Setting (scripted) #7 Game win - Setting (scripted)

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#4 Player - Entity (controllable) #5 Bosses - Entity (autonomous)

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#1 Settings = Stages #2 Entities = Actors

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This looks familiar

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Story?

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Monomyth or “Hero’s Journey”

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Simplified monomyth #1 Major crisis #2 Choosen one #3 Behind enemy lines #4 Insurmountable odds #5 Return home victorious

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Storyboard

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Game mechanics

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Dismissal

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GameJam

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Pygame

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Scanlines

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Scanlines Sprites

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Scanlines Sprites Double buffering

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Scanlines Sprites Double buffering Main loop

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The Main Loop

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The main loop VBlank Interrupt service: ● Process input events ● Update bad guys ● Update good guys ● Update environment ● Paint screen ● Update screen ● Release control

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The main loop BEGIN: ● Process input events ● Update bad guys ● Update good guys ● Update environment ● Paint screen ● Update screen ● GOTO BEGIN

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The main loop BEGIN: ● Process input events ● Update bad guys ● Update good guys ● Update environment ● Paint screen ● Update screen ● GOTO BEGIN

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Actual code

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The main loop class Game(object): def on_setup(self): # Configure screen, resolution, sound, fonts def on_events(self): # Handle input events def on_update(self): # Update entities, movement, behaviour def on_blit(self): # Paint scene and actor in canvas def on_render(self): # Display canvas on screen

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The main loop class Game(object): ... def run(self): self.on_setup() while not self.finish: self.on_events() self.on_update() self.on_blit() # Render pygame.display.flip()

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Setup

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The main loop def on_setup(self) self.clock = pygame.time.Clock() screen_mode = pygame.HWSURFACE | pygame.DOUBLEBUF if self.fullscreen: screen_mode |= pygame.FULLSCREEN self._screen = pygame.display.set_mode(DEFAULT_SCREENSIZE, screen_mode) self.surface = pygame.Surface(self._screen.get_size()) self.running = True self.font = pygame.font.Font(GAME_FONT, 15) self.pause_sound = pygame.mixer.Sound('assets/sounds/pause.wav') self.player = ActorPlayer(game=self) pygame.display.set_caption(GAME_TITLE) self._current_stage = None self.can_be_paused = self._can_be_paused = False self._exit_prompt = False self.ask_exit_confirm = False self.initial_stage = self.module.initial_stage post_event(event=EVENT_CHANGE_STAGE, stage=self.initial_stage)

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Events

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The main loop def on_event(self) for event in pygame.event.get(): try: self.on_event(event) except SwallowEvent: pass else: if self._current_stage: self.module.stages[self._current_stage].on_event(event)

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Updates

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The main loop class Game(object): ... def run(self): self.on_setup() while not self.finish: self.on_events() self.module.stages[self._current_stage].on_update() self.on_blit() # Render pygame.display.flip()

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Blit

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The main loop def on_blit(self): self.module.stages[self._current_stage].on_blit() if self._exit_prompt: self.exit_confirmation(self.font) if self.paused: self.display_pause_label(self.font) if self.shake_screen: self._screen.blit(self.surface, (randint(0, 10), randint(0, 10))) else: self._screen.blit(self.surface, (0, 0))

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Screen refresh

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Double buffering

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Game code Screen

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Game code Screen

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Game code Screen

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Scanlines

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http://lea.hamradio.si/~s51kq/scan-lines.gif

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Game code Screen Memory page 1 Memory page 2

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Game code Screen Memory page 1 Memory page 2 Video generator pointer

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Game code Screen Memory page 1 Memory page 2 Video generator pointer Draw on inactive page

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Game code Screen Memory page 1 Memory page 2 Video generator pointer Draw on inactive page

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Game code Screen Memory page 1 Memory page 2 Switch video generator pointer

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Game code Screen Memory page 1 Memory page 2 Draw on inactive page

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Game code Screen Memory page 1 Memory page 2 Switch video generator pointer

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Stages

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Stage class Stage(object): def __init__(self, next_stage=None): def add_actor(self, actor): def on_blit(self): def on_event(self, event): def on_level_exit(self): def on_setup(self, game): def on_start(self): def on_update(self):

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Stage StageScripted StagePlayable StagePlayableBoss Stage

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class Stage(object): def add_actor(self, actor): if actor not in self.actors: actor.on_setup(stage=self) self.actors.append(actor) def on_blit(self): self.on_draw_background() for actor in self.actors: actor.on_blit() def on_update(self): if not self.game.paused: for actor in self.actors: actor.on_update(time_passed=self.game.time_passed) for time, entry in self._runtime_script.items(): if pygame.time.get_ticks() > self._start_time + time: entry = self._runtime_script.pop(time) entry.on_execute() Stage

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Stage StageScripted StagePlayable StagePlayableBoss Stage

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Stage StageScripted StagePlayable StagePlayableBoss Stage

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class StageScripted(Stage): def on_setup(self, game): ... self.script = {} def on_start(self): self._start_time = pygame.time.get_ticks() self._runtime_script = self.script.copy() def on_update(self): if not self.game.paused: for actor in self.actors: actor.on_update(time_passed=self.game.time_passed) for time, entry in self._runtime_script.items(): if pygame.time.get_ticks() > self._start_time + time: entry = self._runtime_script.pop(time) entry.on_execute() Stage

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class StageTitle(StageScripted): def on_setup(self, *args, **kwargs): super(...) text_press_enter = DisplayText(string=, position=, font_file=, size=, effect=, horizontal_align=, vertical_align=) text_credit = text_version = self.game.can_be_pause = False self.game.ask_exit_confirm = False self.script = { 0000: Background(image_file=, fit=), 0001: PlayMusic(filename=, loop=True), 0002: ActorCommand(text_press_enter, lambda x: x.show()), 0003: ActorCommand(text_credit, lambda x: x.show()), 0004: ActorCommand(text_version, lambda x: x.show()), } Stage

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def on_event(self, event): if event.type == pygame.KEYDOWN: post_event(event=EVENT_CHANGE_STAGE, stage=self.next_stage) Stage

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class StoryStage(StageScripted): def on_setup(self, *args, **kwargs): ... evil_spaceship = ActorSpaceship(game=self.game) tractor_beam = ActorTracktorBeam(game=self.game) book_01 = ActorBook01(game=self.game) book_02 = ActorBook02(game=self.game) book_03 = ActorBook03(game=self.game) book_04 = ActorBook04(game=self.game) book_05 = ActorBook05(game=self.game) human_ship = ActorHumanShip(game=self.game) text_time = DisplayText(string=TEXT_YEAR, position=(0, 400), effect=TypeWriter (150, 'assets/sounds/08.ogg'), horizontal_align=CenterAlign) text_book_1 = DisplayText(string=TEXT_STEAL_BOOKS_1, position=(0, 350), effect=TypeWriter(50), horizontal_align=CenterAlign) text_book_2 = DisplayText(string=TEXT_STEAL_BOOKS_2, position=(0, 380), effect=TypeWriter(50), horizontal_align=CenterAlign) text_hero = DisplayText(string=TEXT_HERO, position=(0, 350), effect=TypeWriter (50), horizontal_align=CenterAlign) Stage

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class StoryStage(StageScripted): def on_setup(self, *args, **kwargs): ... self.script = { 0000: Background(image_file='assets/backgrounds/earth.png'), 0001: PlayMusic('assets/music/LongDarkLoop.ogg'), 1000: ActorCommand(text_time, lambda x: x.show()), 6000: ActorCommand(text_time, lambda x: x.hide()), 6500: ActorCommand(text_book_1, lambda x: x.show()), 9000: ActorCommand(text_book_2, lambda x: x.show()), 15000: ActorCommand(text_book_1, lambda x: x.hide()), 15001: ActorCommand(text_book_2, lambda x: x.hide()), 16500: ActorCommand(evil_spaceship, lambda x: x.set_position(220, -65)), 16501: ActorCommand(evil_spaceship, lambda x: x.show()), 16502: ActorCommand(evil_spaceship, lambda x: x.set_destination(235, 30, 0.04)), 17500: ActorCommand(evil_spaceship, lambda x: x.set_destination(235, 30, 0.03)), 19000: ActorCommand(evil_spaceship, lambda x: x.set_destination(235, 30, 0.01)),

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class StoryStage(StageScripted): def on_setup(self, *args, **kwargs): ... self.script = … 21000: ActorCommand(tractor_beam, lambda x: x.set_position(253, 70)), 21001: ActorCommand(tractor_beam, lambda x: x.show()), 21200: ActorCommand(tractor_beam, lambda x: x.strobe_start()), 22100: ActorCommand(book_01, lambda x: x.set_destination(240, 40, 0.02)), 22101: ActorCommand(book_01, lambda x: x.set_position(253, 170)), 22102: ActorCommand(book_01, lambda x: x.show()),

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Actors

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Actors class Actor(object): animation_death_file = None animation_death_fps = 8 animation_loop = True animation_normal_files = [] attack_points = 1 total_hit_points = 100 invincible = False fps = 1 sound_hit_file = None sound_die_file = None speed = 0.05 team = None scale = 1 rotation = 0 flip_x = False flip_y = False can_overflow = True

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Actors def __init__(self, game): def change_animation(self, images): def destroy(self): def hide(self): def is_alive(self): def set_animation_fps(self, fps): def set_destination(self, x_position, y_position, speed): def set_direction(self, vector): def set_flip_x(self, flip): def set_flip_y(self, flip): def set_invincible(self, offset): def set_position(self, x_position, y_position): def set_rotation(self, degrees): def set_scale(self, scale): def show(self): def strobe_start(self): def strobe_stop(self):

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Actors @staticmethod def load_sliced_sprites(width, height, filename, origin_y=0): File Memory self.images = []

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Actors

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Actors def set_animation_fps(self, fps): self._animation_delay = 1000 / fps def on_animate(self): if self.animation_active or force: t = pygame.time.get_ticks() if t - self._last_update > self._animation_delay: self._frame += 1 if self._frame >= len(self.images): if self.animation_loop: self._frame = 0 else: self._frame -= 1 self.on_animation_finished() self.image = self.images[self._frame] self._last_update = t

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Actors def is_alive(self): return self.hit_points > 0 def change_animation(self, images): self.images = images self._frame = -1 self._last_update = 0 self.rect = self.images[0].get_rect() self.size = self.images[0].get_size() self.image = self.images[0]

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Actors def on_hit(self, attack_points): self.hit_points -= attack_points if self.sound_hit: self.sound_hit.play() if self.hit_points <= 0: self.hit_points = 0 self.on_death() def on_death(self): self.hit_points = 0 self.direction = vec2d(0, 0) if self.sound_die: self.sound_die.play() self.animation_loop = False if self.animation_death_fps: self.set_animation_fps(self.animation_death_fps) if self.animation_death: self.change_animation(self.animation_death)

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Actors def on_animate(self, time_passed, force=False): def on_animation_finished(self): def on_blit(self): def on_calculate_movement(self): def on_collision(self, foreign_actor): def on_death(self): def on_execute(self): def on_event(self, event): def on_hit(self, attack_points): def on_setup(self, stage): def on_update(self, time_passed, force=False):

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Displacement (how much movement) Position (where)

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Position (where) Direction vector * time Displacement (how much movement)

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Position (where)

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Direction vector

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Direction vector

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Vec2D

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new_position = old_position + vector * speed * time_delta time_delta = current_time - last_calculation_time

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new_position = old_position + vector * speed * time_delta time_delta = [given by pygame]

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new_position = old_position + vector * speed * time_delta

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new_position = old_position + vector * speed

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vector * speed

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vector

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Player = Moves by keyboard Enemy = Follows player Boss = Bounces

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class Actor(object): def set_direction(self, vector): self.direction = vector def on_update(self, time_passed, force=False): if self.is_alive(): self.on_calculate_movement() displacement = vec2d( self.direction.x * self.speed * time_passed, self.direction.y * self.speed * time_passed ) self.pos += displacement

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class ActorPlayer(Actor): def on_calculate_movement(self): super(ActorPlayer, self).on_calculate_movement() if self.game.running and self.is_alive(): keys_pressed = pygame.key.get_pressed() direction_y = 0 direction_x = 0 if keys_pressed[pygame.K_LEFT]: direction_x = -1 if keys_pressed[pygame.K_RIGHT]: direction_x = 1 if keys_pressed[pygame.K_UP]: direction_y = -1 if keys_pressed[pygame.K_DOWN]: direction_y = 1 self.set_direction(vec2d(direction_x, direction_y).normalized())

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class ActorEnemy(Actor): def on_calculate_movement(self): # Follow player self.set_direction((self.game.player.pos - self.pos).normalized())

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5 * -1 = -5 -5 * -1 = 5 -1 ~ NOT

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from libraries.vec2d import vec2d >>> vec2d(1, 0) * vec2d(-1, 1) # Moves right, invert (x) vec2d(-1, 0) # Now moves left >>> vec2d(-1, 0) * vec2d(-1, 1) # Moves left, invert (x) vec2d(1, 0) # Now moves right >>> vec2d(0, -1) * vec2d(-1, 1) # Moves up, invert (x) vec2d(0, -1) # Keeps moving up

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class ActorBoss(Actor): def on_calculate_movement(self): bounds_rect = self.game.surface.get_rect() if self.rect.left <= bounds_rect.left: self.direction.x *= -1 elif self.rect.right >= bounds_rect.right: self.direction.x *= -1 elif self.rect.top <= bounds_rect.top: self.direction.y *= -1 elif self.rect.bottom >= bounds_rect.bottom: self.direction.y *= -1

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Demo

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Questions? @siloraptor [email protected] https://github.com/rosarior http://robertorosario.com

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Thank you! @siloraptor [email protected] https://github.com/rosarior http://robertorosario.com