Terminal–based game tutorial

0_README.md

Sources for my blog post about terminal–based game

1_game.rb

class Game
  SLEEP_INTERVAL = 0.2

  def run
    loop do
      draw_screen
      sleep SLEEP_INTERVAL
    end
  end

  private

  def draw_screen
    system "clear"

    puts Time.now
  end
end

Game.new.run

2_game.rb

TREE, SPACE = '🌲', "・"

Level = Struct.new(:map, :enemies, :player, :door)

class LevelBuilder
  def initialize(filepath)
    @filepath = filepath
  end

  MAPPING = { 't' => TREE, 's' => SPACE }

  def build
    Level.new.tap do |level|
      level.enemies = []

      level.map = File.readlines(@filepath).map do |line|
        line.sub("\n", "").chars.map do |c|
          MAPPING[c] || SPACE
        end
      end
    end
  end
end

class Game
  SLEEP_INTERVAL = 0.2

  def run
    @level = LevelBuilder.new("./map.txt").build

    loop do
      draw_screen
      sleep SLEEP_INTERVAL
    end
  end

  private

  def draw_screen
    system "clear"

    @level.each do |row|
      row.each do |cell|
        print cell
      end
      puts
    end
  end
end

Game.new.run

3_game.rb

PLAYER, ENEMY, DOOR, TREE, SPACE = '🧙', '👻', '🚪', '🌲', "・"

Level = Struct.new(:map, :enemies, :player, :door)

DynamicObject = Struct.new(:row_idx, :col_idx, :kind)

class LevelBuilder
  def initialize(filepath)
    @filepath = filepath
  end

  MAPPING = { 't' => TREE, 's' => SPACE }

  def build
    Level.new.tap do |level|
      level.enemies = []

      level.map = File.readlines(@filepath).map.with_index do |line, row_idx|
        line.chars.map.with_index do |c, col_idx|
          case c
          when 'e'
            level.enemies << DynamicObject.new(row_idx, col_idx, :enemy)
            SPACE
          when 'p'
            level.player = DynamicObject.new(row_idx, col_idx, :player)
            SPACE
          when 'd'
            level.door = DynamicObject.new(row_idx, col_idx, :door)
            SPACE
          else
            MAPPING[c]
          end
        end
      end
    end
  end
end

class Game
  SLEEP_INTERVAL = 0.2

  def run
    @level = LevelBuilder.new("./map.txt").build

    loop do
      draw_screen
      sleep SLEEP_INTERVAL
    end
  end

  private

  def draw_screen
    system "clear"

    @level.map.each_with_index do |row, row_idx|
      row.each_with_index do |cell, col_idx|
        if @level.player.row_idx == row_idx && @level.player.col_idx == col_idx
          print PLAYER
        elsif @level.door.row_idx == row_idx && @level.door.col_idx == col_idx
          print DOOR
        elsif @level.enemies.find { |enemy| enemy.row_idx == row_idx && enemy.col_idx == col_idx }
          print ENEMY
        else
          print cell
        end
      end
      puts "\n"
    end
  end
end

Game.new.run

4_game.rb

PLAYER, ENEMY, DOOR, TREE, SPACE = '🧙', '👻', '🚪', '🌲', "・"

Level = Struct.new(:map, :enemies, :player, :door)

UP, DOWN, RIGHT, LEFT = 119, 115, 100, 97

DynamicObject = Struct.new(:row_idx, :col_idx, :kind) do
  def move(dir)
    case dir
    when RIGHT then self.col_idx += 1
    when LEFT then self.col_idx -= 1
    when UP then self.row_idx -= 1
    when DOWN then self.row_idx += 1
    end
  end
end

class LevelBuilder
  def initialize(filepath)
    @filepath = filepath
  end

  MAPPING = { 't' => TREE, 's' => SPACE }

  def build
    Level.new.tap do |level|
      level.enemies = []

      level.map = File.readlines(@filepath).map.with_index do |line, row_idx|
        line.chars.map.with_index do |c, col_idx|
          case c
          when 'e'
            level.enemies << DynamicObject.new(row_idx, col_idx, :enemy)
            SPACE
          when 'p'
            level.player = DynamicObject.new(row_idx, col_idx, :player)
            SPACE
          when 'd'
            level.door = DynamicObject.new(row_idx, col_idx, :door)
            SPACE
          else
            MAPPING[c]
          end
        end
      end
    end
  end
end

class Game
  SLEEP_INTERVAL = 0.2

  def run
    @level = LevelBuilder.new("./map.txt").build

    loop do
      draw_screen

      new_player_position = DynamicObject.new(@level.player.row_idx, @level.player.col_idx, :player)
      new_player_position.move(get_pressed_key)

      @level.player = new_player_position

      sleep SLEEP_INTERVAL
    end
  end

  private

  def draw_screen
    system "clear"

    @level.map.each_with_index do |row, row_idx|
      row.each_with_index do |cell, col_idx|
        if @level.player.row_idx == row_idx && @level.player.col_idx == col_idx
          print PLAYER
        elsif @level.door.row_idx == row_idx && @level.door.col_idx == col_idx
          print DOOR
        elsif @level.enemies.find { |enemy| enemy.row_idx == row_idx && enemy.col_idx == col_idx }
          print ENEMY
        else
          print cell
        end
      end
      puts "\n"
    end
  end

  def get_pressed_key
    begin
      system('stty raw -echo')
      (STDIN.read_nonblock(4).ord rescue nil)
    ensure
      system('stty -raw echo')
    end
  end
end

Game.new.run

5_game.rb

PLAYER, ENEMY, DOOR, TREE, SPACE = '🧙', '👻', '🚪', '🌲', "・"

Level = Struct.new(:map, :enemies, :player, :door)

UP, DOWN, RIGHT, LEFT = 119, 115, 100, 97

DynamicObject = Struct.new(:row_idx, :col_idx, :kind) do
  def move(dir)
    case dir
    when RIGHT then self.col_idx += 1
    when LEFT then self.col_idx -= 1
    when UP then self.row_idx -= 1
    when DOWN then self.row_idx += 1
    end
  end
end

class LevelBuilder
  def initialize(filepath)
    @filepath = filepath
  end

  MAPPING = { 't' => TREE, 's' => SPACE }

  def build
    Level.new.tap do |level|
      level.enemies = []

      level.map = File.readlines(@filepath).map.with_index do |line, row_idx|
        line.chars.map.with_index do |c, col_idx|
          case c
          when 'e'
            level.enemies << DynamicObject.new(row_idx, col_idx, :enemy)
            SPACE
          when 'p'
            level.player = DynamicObject.new(row_idx, col_idx, :player)
            SPACE
          when 'd'
            level.door = DynamicObject.new(row_idx, col_idx, :door)
            SPACE
          else
            MAPPING[c]
          end
        end
      end
    end
  end
end

class Game
  SLEEP_INTERVAL = 0.2

  def run
    @level = LevelBuilder.new("./map.txt").build

    loop do
      draw_screen

      new_player_position = DynamicObject.new(@level.player.row_idx, @level.player.col_idx, :player)
      new_player_position.move(get_pressed_key)

      case check_collision(new_player_position.row_idx, new_player_position.col_idx, @level.enemies + [@level.door])
      when :door
        puts "🎉 Level passed 🎉"
        break
      when :enemy
        puts "☠️ You died ☠️"
        break
      when nil
        @level.player = new_player_position
      end

      sleep SLEEP_INTERVAL
    end
  end

  private

  def draw_screen
    system "clear"

    @level.map.each_with_index do |row, row_idx|
      row.each_with_index do |cell, col_idx|
        if @level.player.row_idx == row_idx && @level.player.col_idx == col_idx
          print PLAYER
        elsif @level.door.row_idx == row_idx && @level.door.col_idx == col_idx
          print DOOR
        elsif @level.enemies.find { |enemy| enemy.row_idx == row_idx && enemy.col_idx == col_idx }
          print ENEMY
        else
          print cell
        end
      end
      puts "\n"
    end
  end

  def get_pressed_key
    begin
      system('stty raw -echo')
      (STDIN.read_nonblock(4).ord rescue nil)
    ensure
      system('stty -raw echo')
    end
  end

  def check_collision(row_idx, col_idx, objects)
    return :out_of_border if row_idx < 0 || row_idx >= @level.map.length || col_idx < 0 || col_idx >= @level.map[0].length
    return :tree if @level.map[row_idx][col_idx] == TREE
    objects.find { _1.row_idx == row_idx && _1.col_idx == col_idx }&.kind
  end
end

Game.new.run

6_game.rb

PLAYER, ENEMY, DOOR, TREE, SPACE = '🧙', '👻', '🚪', '🌲', "・"

Level = Struct.new(:map, :enemies, :player, :door)

UP, DOWN, RIGHT, LEFT = 119, 115, 100, 97

DynamicObject = Struct.new(:row_idx, :col_idx, :kind) do
  def move(dir)
    case dir
    when RIGHT then self.col_idx += 1
    when LEFT then self.col_idx -= 1
    when UP then self.row_idx -= 1
    when DOWN then self.row_idx += 1
    end
  end
end

class LevelBuilder
  def initialize(filepath)
    @filepath = filepath
  end

  MAPPING = { 't' => TREE, 's' => SPACE }

  def build
    Level.new.tap do |level|
      level.enemies = []

      level.map = File.readlines(@filepath).map.with_index do |line, row_idx|
        line.chars.map.with_index do |c, col_idx|
          case c
          when 'e'
            level.enemies << DynamicObject.new(row_idx, col_idx, :enemy)
            SPACE
          when 'p'
            level.player = DynamicObject.new(row_idx, col_idx, :player)
            SPACE
          when 'd'
            level.door = DynamicObject.new(row_idx, col_idx, :door)
            SPACE
          else
            MAPPING[c]
          end
        end
      end
    end
  end
end

class Game
  SLEEP_INTERVAL = 0.2

  def run
    @level = LevelBuilder.new("./map.txt").build

    loop do
      move_enemies
      draw_screen

      case check_collision(@level.player.row_idx, @level.player.col_idx, @level.enemies)
      when :enemy
        puts "☠️ You died ☠️"
        break
      end

      new_player_position = DynamicObject.new(@level.player.row_idx, @level.player.col_idx, :player)
      new_player_position.move(get_pressed_key)

      case check_collision(new_player_position.row_idx, new_player_position.col_idx, @level.enemies + [@level.door])
      when :door
        puts "🎉 Level passed 🎉"
        break
      when :enemy
        puts "☠️ You died ☠️"
        break
      when nil
        @level.player = new_player_position
      end

      sleep SLEEP_INTERVAL
    end
  end

  private

  def draw_screen
    system "clear"

    @level.map.each_with_index do |row, row_idx|
      row.each_with_index do |cell, col_idx|
        if @level.player.row_idx == row_idx && @level.player.col_idx == col_idx
          print PLAYER
        elsif @level.door.row_idx == row_idx && @level.door.col_idx == col_idx
          print DOOR
        elsif @level.enemies.find { |enemy| enemy.row_idx == row_idx && enemy.col_idx == col_idx }
          print ENEMY
        else
          print cell
        end
      end
      puts "\n"
    end
  end

  def get_pressed_key
    begin
      system('stty raw -echo')
      (STDIN.read_nonblock(4).ord rescue nil)
    ensure
      system('stty -raw echo')
    end
  end

  def check_collision(row_idx, col_idx, objects)
    return :out_of_border if row_idx < 0 || row_idx >= @level.map.length || col_idx < 0 || col_idx >= @level.map[0].length
    return :tree if @level.map[row_idx][col_idx] == TREE
    objects.find { _1.row_idx == row_idx && _1.col_idx == col_idx }&.kind
  end

  def move_enemies
    @level.enemies.each_with_index do |enemy, idx|
      next if rand(1) > 0.8

      new_enemy = DynamicObject.new(enemy.row_idx, enemy.col_idx, :enemy)
      new_enemy.move([RIGHT, LEFT, UP, DOWN].sample)
      @level.enemies[idx] = new_enemy if check_collision(new_enemy.row_idx, new_enemy.col_idx, [@level.door, @level.player]).nil?
    end
  end
end

Game.new.run

7_game.rb

PLAYER, ENEMY, DOOR, TREE, SPACE = '🧙', '👻', '🚪', '🌲', "・"

Level = Struct.new(:map, :enemies, :player, :door)

UP, DOWN, RIGHT, LEFT = 119, 115, 100, 97

DynamicObject = Struct.new(:row_idx, :col_idx, :kind) do
  def move(dir)
    case dir
    when RIGHT then self.col_idx += 1
    when LEFT then self.col_idx -= 1
    when UP then self.row_idx -= 1
    when DOWN then self.row_idx += 1
    end
  end
end

class LevelBuilder
  def initialize(filepath)
    @filepath = filepath
  end

  MAPPING = { 't' => TREE, 's' => SPACE }

  def build
    Level.new.tap do |level|
      level.enemies = []

      level.map = File.readlines(@filepath).map.with_index do |line, row_idx|
        line.strip.chars.map.with_index do |c, col_idx|
          case c
          when 'e'
            level.enemies << DynamicObject.new(row_idx, col_idx, :enemy)
            SPACE
          when 'p'
            level.player = DynamicObject.new(row_idx, col_idx, :player)
            SPACE
          when 'd'
            level.door = DynamicObject.new(row_idx, col_idx, :door)
            SPACE
          else
            MAPPING[c]
          end
        end
      end
    end
  end
end

class Screen
  def render_level(level)
    system "clear"

    level.map.each_with_index do |row, row_idx|
      row.each_with_index do |cell, col_idx|
        if level.player.row_idx == row_idx && level.player.col_idx == col_idx
          print PLAYER
        elsif level.door.row_idx == row_idx && level.door.col_idx == col_idx
          print DOOR
        elsif level.enemies.find { |enemy| enemy.row_idx == row_idx && enemy.col_idx == col_idx }
          print ENEMY
        else
          print cell
        end
      end
      puts "\n"
    end
  end

  def render_death_message = puts "☠️ You died ☠️"
  def render_level_passed_message = puts "🎉 Level passed 🎉"
end

class Game
  SLEEP_INTERVAL = 0.2

  def run
    screen = Screen.new

    @level = LevelBuilder.new("./map.txt").build

    loop do
      move_enemies
      screen.render_level(@level)

      case check_collision(@level.player.row_idx, @level.player.col_idx, @level.enemies)
      when :enemy
        screen.render_death_message
        break
      end

      new_player_position = DynamicObject.new(@level.player.row_idx, @level.player.col_idx, :player)
      new_player_position.move(get_pressed_key)

      case check_collision(new_player_position.row_idx, new_player_position.col_idx, @level.enemies + [@level.door])
      when :door
        screen.render_level_passed_message
        break
      when :enemy
        screen.render_death_message
        break
      when nil
        @level.player = new_player_position
      end

      sleep SLEEP_INTERVAL
    end
  end

  private

  def get_pressed_key
    begin
      system('stty raw -echo')
      (STDIN.read_nonblock(4).ord rescue nil)
    ensure
      system('stty -raw echo')
    end
  end

  def check_collision(row_idx, col_idx, objects)
    return :out_of_border if row_idx < 0 || row_idx >= @level.map.length || col_idx < 0 || col_idx >= @level.map[0].length
    return :tree if @level.map[row_idx][col_idx] == TREE
    objects.find { _1.row_idx == row_idx && _1.col_idx == col_idx }&.kind
  end

  def move_enemies
    @level.enemies.each_with_index do |enemy, idx|
      next if rand(1) > 0.8

      new_enemy = DynamicObject.new(enemy.row_idx, enemy.col_idx, :enemy)
      new_enemy.move([RIGHT, LEFT, UP, DOWN].sample)
      @level.enemies[idx] = new_enemy if check_collision(new_enemy.row_idx, new_enemy.col_idx, [@level.door]).nil?
    end
  end
end

Game.new.run

Several corrections for 7_game.rb.

Line 30:
Instead of

line.chars.map.with_index do |c, col_idx|

should be

line.strip.chars.map.with_index do |c, col_idx|

Otherwise it adds one nil at the end of each row, so the enemy can step outside of level.

Line 92:
Instead of

new_player_position = DynamicObject.new(@level.player.row_idx, @level.player.col_idx)

should be

new_player_position = DynamicObject.new(@level.player.row_idx, @level.player.col_idx, :player)

Without it the collision detection works incorrectly on line 124
objects.find { _1.row_idx == row_idx && _1.col_idx == col_idx }&.kind
will return nil instead of :player)

Line 133:

@level.enemies[idx] = new_enemy if check_collision(new_enemy.row_idx, new_enemy.col_idx, [@level.door, @level.player]).nil?

should be

@level.enemies[idx] = new_enemy if check_collision(new_enemy.row_idx, new_enemy.col_idx, [@level.door]).nil?

since the enemy can move to player's position and kill it. With it, the enemy will forever avoid the player as an obstacle.

@airled thank you so much, updated gist and the post 👏