public void loadLevel( String file_name ) throws IOException {
        InputStream is =
            Level.class.getResourceAsStream( "resources/" + file_name );
        BufferedReader br = new BufferedReader( new InputStreamReader( is ) );
        String line = br.readLine();
        
        int cell_pos_x = 0, cell_pos_y = 0;
        while ( line != null ) {
            for ( String cell_type : line.split( "\\s+" ) ) {
                switch ( cell_type ) {
                    case "e":
                        field[cell_pos_y][cell_pos_x] = "empty";
                        break;
                    case "b":
                        field[cell_pos_y][cell_pos_x] = "brick";
                        break;
                    case "t":
                        targets++;
                        field[cell_pos_y][cell_pos_x] = "target";
                        break;
                    case "s":
                        swapper_x = cell_pos_x;
                        swapper_y = cell_pos_y;
                        field[cell_pos_y][cell_pos_x] = "swapper";
                        break;
                    case "h":
                        hunter_x = cell_pos_x;
                        hunter_y = cell_pos_y;
                        field[cell_pos_y][cell_pos_x] = "hunter";
                        break;
                        
                    default:
                        throw new IOException( "Illegal symbol in " + file_name );
                }
                cell_pos_x++;
            }
            cell_pos_y++;
            cell_pos_x = 0;
            line = br.readLine();
        }
        br.close();
    }