Activities/Turtle in a Pond

Turtle in a Pond Activity

Turtle in a Pond is a strategy game. The goal is to surround the turtle before it runs off the screen.

How to play Turtle in a Pond

Click on the dots to keep the turtle from escaping.

• 

  The turtle is captured

• 

  The turtle escaped

Did you know that:

• You can load your own strategy for the turtle by importing Python code you can write with Pippy?

The Toolbars

from left to right

1. the Activity toolbar button (shown in the open position)
2. the New-game button
3. an area for messages
4. the Load-new-strategy button
5. the Reload-the-default-strategy button
6. the Activity stop button

Strategy

Cut and paste these examples into Pippy and save then to your Sugar Journal. Then use the Load-new-strategy button in the Turtle-in-a-Pond Activity to try them.

In this strategy, the turtle moves down regardless of whether the dot is open.

def _turtle_strategy(self, turtle):
    turtle[1] += 1
    return turtle

In this strategy, the turtle moves down until it is blocked (i.e., when the dot type is True).

def _turtle_strategy(self, turtle):
    if not self._dots[self._grid_to_dot((turtle[0], turtle[1]+1))].type:
       turtle[1] += 1
    return turtle

In this strategy, the turtle searches for an open dot, looking clockwise.

def _turtle_strategy(self, turtle):
    dots = self._surrounding_dots(turtle)
    for i in range(6):  # search for an opening
        if not self._dots[dots[i]].type:
            return self._dot_to_grid(dots[i])
    return turtle

In this version, the turtle orientation is set as well.

def _turtle_strategy(self, turtle):
    dots = self._surrounding_dots(turtle)
    for i in range(6):  # search for an opening
        if not self._dots[dots[i]].type:
            self._orientation = i
            return self._dot_to_grid(dots[i])
    return turtle

The turtle choose a random direction and goes there if the dot is open.

def _turtle_strategy(self, turtle):
    dots = self._surrounding_dots(turtle)
    n = int(uniform(0, 6))  # choose a random orientation
    for i in range(6):  # search for an opening
        if not self._dots[dots[(i + n) % 6]].type:
            self._orientation = (i + n) % 6
            return self._dot_to_grid(dots[(i + n) % 6])
    return turtle

In this strategy, the turtle will go off the edge if it can.

def _turtle_strategy(self, turtle):
    dots = self._surrounding_dots(turtle)
    for i in range(6):  # search for an edge
        if self._dots[dots[i]].type is None:
            self._orientation = i
            return self._dot_to_grid(dots[i])

    n = int(uniform(0, 6))  # choose a random orientation
    for i in range(6):  # search for an opening
        if not self._dots[dots[(i + n) % 6]].type:
            self._orientation = (i + n) % 6
            return self._dot_to_grid(dots[(i + n) % 6])
    return turtle

In this version, it looks for a path to the edge in the direction it was already heading.

def _turtle_strategy(self, turtle):
    dots = self._surrounding_dots(turtle)

    for i in range(6):  # search for an edge
        if self._dots[dots[i]].type is None:
            self._orientation = i
            return self._dot_to_grid(dots[i])

    if self._daylight_ahead(turtle):
        return self._dot_to_grid(dots[self._orientation])

    n = int(uniform(0, 6))  # choose a random orientation
    for i in range(6):  # search for an opening
        if not self._dots[dots[(i + n) % 6]].type:
            self._orientation = (i + n) % 6
            return self._dot_to_grid(dots[(i + n) % 6])
    return turtle

In the default strategy, a weighing function is used: preference is given to dots closer to the edges.

def _turtle_strategy(self, turtle):
    dots_ordered_by_weight = self._ordered_weights(turtle)
    if self._dots[dots_ordered_by_weight[0]].type is None:
        return self._dot_to_grid(dots_ordered_by_weight[0])
    elif not self._dots[dots_ordered_by_weight[0]].type:
        return self._dot_to_grid(dots_ordered_by_weight[0])
    else:
        return turtle

The dots are stored in a 13✕13 array. Each dot has an attribute, 'type', that determines it status. The edges have a type=None. Occupied dots have a type=True. Unoccupied dots have a type=False.

Your strategy should start with:

def _turtle_strategy(self, turtle):

The turtle argument is a tuple containing the column and row of the current turtle position. That is, turtle[0] is the horizontal position and turtle[1] is the vertical position.

Your strategy should return a tuple containing the column and row of the new turtle position, e.g.,

return [column, row]

Resources

There are some resources that you can use in your program, including:

self._surrounding_dots((column, row))

returns an array of dots surrounding a given position in the grid

self._daylight_ahead((column, row))

returns True if there is a clear path to the edge heading in the current direction

self._ordered_weights((column, row))

returns an array of surrounding dots ordered by their distance from the edge

self._dots

the array of dots from which you can test the type attribute (self._dots[i].type==None → edge; self._dots[i].type==False → open; self._dots[i].type==True → blocked)

self._orientation

you can set the orientation of your turtle by assigning a number from 0-5 (clockwise beginning with 30 degrees from north)

self._set_label('your message here')

you can write a message on the toolbar if you want to communicate what your turtle is thinking

self._grid_to_dot((column, row))

returns the dot that is at a grid position (column, row)

self._dot_to_grid(dot)

returns an array (column, row) representing the grid position of a dot

Digging deeper

To better understand how to use the above resources, view the program source, look at game.py for code relating to game strategy. View_Source

If your Sugar distribution includes the Gnome editor GEdit, you can use it to view and edit the program source. In terminal type

gedit

You will find the program source at

/home/olpc/Activities/TurtleinaPond.activity

See Modifing_an_Activity#Editing for other methods for viewing and editing the source.

Where to get Turtle in a Pond

The Turtle in a Pond activity is available for download from the Sugar activity portal: Turtle in a Pond

The source code is available on the Sugar Labs Gitorious server.