Just the code to slice a sprite sheet up and move the character. It needs the spritesheet to work, I'll publish a repo if you want to try it out.

character-mover.rb

class Char < Hokusai::Block
  template do
    child(Hokusai::Blocks::Empty) do
      on(:keydown) do |event|
        move(event)
      end
    end
  end

  # 68x68 blocks
  def initialize(**args)
    @x = 0.0
    @y = 0.0
    @sprite_index = 0

    super
  end

  def sprite(index)
    @rects ||= begin
      arr = []
      row = 0.0
      col = 0.0
      
      while row < 1024
        while col < 1024
          arr << Hokusai::Rect.new(col, row, 64.0, 64.0)

          col += 64
        end

        col = 0.0
        row += 64
      end

      arr
    end

    @rects[index]
  end

  def move(event)
    case event.key
    when :left
      @x -= 5.0
    when :up
      @y -= 5.0
    when :down
      @y += 5.0
      case @sprite_index
      when 48
        @sprite_index = 49
      when 49
        @sprite_index = 50
      else
        @sprite_index = 48
      end
    when :right
      @x += 5.0
      case @sprite_index
      when 64
        @sprite_index = 65
      when 65
        @sprite_index = 66
      when 66
        @sprite_index = 67
      when 67
        @sprite_index = 68
      when 68
        @sprite_index = 69
      else
        @sprite_index = 64
      end
    end
  end

  def render(canvas)
    canvas.x = @x
    canvas.y = @y

    draw do
      image(Hokusai.images.get("body"), @x, @y, 64.0, 64.0) do |command|
        command.slice = sprite(@sprite_index)
      end
    end

    yield canvas
  end
end

class Map < Hokusai::Block
  template do
    child(Char) do
      prop :width, 64.0
      prop :height, 64.0

      on(:click) do
        puts "hello"
      end
    end
  end
end

class Game < Hokusai::Block
  template <<~EOF
  [template]
    map
  EOF

  uses(map: Map)
end

Hokusai::Backend.run(Game) do |config|
  config.title = "Okay"
  config.fps = 60
  config.after_load do
    Hokusai.images.register "body", Hokusai::Image.from_file("assets/body.png")
  end
end