A _room_ describes a specific location in the game world. Being an abstract concept, it can represent any area of game content that is convenient to group together. In this lesson we will also create a small in-game automap.
In EvAdventure, we will have two main types of rooms:
- Normal, above-ground rooms. Based on a fixed map, these will be created once and then don't change. We'll cover them in this lesson.
- Dungeon rooms - these will be examples of _procedurally generated_ rooms, created on the fly as the players explore the underworld. Being subclasses of the normal room, we'll get to them in the [Dungeon generation lesson](./Beginner-Tutorial-Dungeon.md).
The return of `get_display_footer` will show after the [main room description](../../../Components/Objects.md#changing-an-objects-appearance), showing that the room is a sparring room. This means that when a player drops to 0 HP, they will lose the combat, but don't stand any risk of dying (weapons wear out normally during sparring though).
The string returned from `get_display_header` will end up at the top of the [room description](../../../Components/Objects.md#changing-an-objects-description), a good place to have the map appear!
- **Line 12**: The map itself consists of the 2D matrix `_MAP_GRID`. This is a 2D area described by a list of Python lists. To find a given place in the list, you first first need to find which of the nested lists to use, and then which element to use in that list. Indices start from 0 in Python. So to draw the `o` symbol for the southermost room, you'd need to do so at `_MAP_GRID[4][2]`.
- **Line 19**: The `_EXIT_GRID_SHIFT` indicates the direction to go for each cardinal exit, along with the map symbol to draw at that point. So `"east": (1, 0, "-")` means the east exit will be drawn one step in the positive x direction (to the right), using the "-" symbol. For symbols like `|` and "\\" we need to escape with a double-symbol since these would otherwise be interpreted as part of other formatting.
- **Line 51**: We start by making a `deepcopy` of the `_MAP_GRID`. This is so that we don't modify the original but always have an empty template to work from.
- **Line 52**: We use `@` to indicate the location of the player (at coordinate `(2, 2)`). We then take the actual exits from the room use their names to figure out what symbols to draw out from the center.
- **Line 58**: We want to be able to get on/off the grid if so needed. So if a room has a non-cardinal exit in it (like 'back' or up/down), we'll indicate this by showing the `>` symbol instead of the `@` in your current room.
- **Line 67**: Once we have placed all the exit- and room-symbols in the grid, we merge it all together into a single string. At the end we use Python's standard [join](https://www.w3schools.com/python/ref_string_join.asp) to convert the grid into a single string. In doing so we must flip the grid upside down (reverse the outermost list). Why is this? If you think about how a MUD game displays its data - by printing at the bottom and then scrolling upwards - you'll realize that Evennia has to send out the top of your map _first_ and the bottom of it _last_ for it to show correctly to the user.
Normally the room is static until you do something in it. But let's say you are in a room described to be a bustling market. Would it not be nice to occasionally get some random messages like
"You hear a merchant calling out his wares."
"The sound of music drifts over the square from an open tavern door."
"The sound of commerse rises and fall in a steady rythm."
Here's an example of how to accomplish this:
```{code-block} python
:linenos:
:emphasize-lines: 22,25
# in evadventure/rooms.py
# ...
from random import choice, random
from evennia import TICKER_HANDLER
# ...
class EchoingRoom(EvAdventureRoom):
"""A room that randomly echoes messages to everyone inside it"""
The [TickerHandler](../../../Components/TickerHandler.md). This is acts as a 'please tick me - subscription service'. In **Line 22** we tell add our `.send_echo` method to the handler and tell the TickerHandler to call that method every `.echo_rate` seconds.
When the `.send_echo` method is called, it will use `random.random()` to check if we should _actually_ do anything. In our example we only show a message 10% of the time. In that case we use Python's `random.choice()` to grab a random text string from the `.echoes` list to send to everyone inside this room.
> set here/echoes = ["You hear a merchant shouting", "You hear the clatter of coins"]
> py here.start_echo()
If you wait a while you'll eventually see one of the two echoes show up. Use `py here.stop_echo()` if you want.
It's a good idea to be able to turn on/off the echoes at will, if nothing else because you'd be surprised how annoying they can be if they show too often.
In this example we had to resort to `py` to activate/deactivate the echoes, but you could very easily make little utility [Commands](../Part1/Beginner-Tutorial-Adding-Commands.md) `startecho` and `stopecho` to do it for you. This we leave as a bonus exercise.
In this lesson we manipulated strings and made a map. Changing the description of an object is a big part of changing the 'graphics' of a text-based game, so checking out the [parts making up an object description](../../../Components/Objects.md#changing-an-objects-description) is good extra reading.
