021-snake-game/docs/dictionary.md

Domain Dictionary: Snake Game (Day 21)

Metadata

Key	Value
ID	DICT-001
CrossReference	BC-001, SA-001
Language	en
Domain	it

Version History

Date	Status	Author	Reviewer	Change	Commit
2026-10-08	Accepted	Jens Tirsvad Nielsen	S01	Initial version, reviewed in RC-003 (Go)	pending

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Purpose and Scope

Maps each Product Owner (PO) term to its professional information technology (IT) term. PO language: en (domain it), from the registry's Languages section. The PO terms are the words of the lectures of days 20 and 21 as the planning documents use them; the IT terms are the names in the code. The dictionary covers the vocabulary of the game; it exists so that the planning documents use one word for one thing and so that S02 can find the lectures' names in the code. It is adopted from the dictionary of the day-20 repository and gains the terms refresh and inheritance, which the day-21 lectures introduce.

Dictionary

PO term	Language	IT term	Definition	Used as PO term in	Used as IT term in
window	en	Tk window	The desktop window that holds the screen and is opened when the game starts.	BC, SA, PP, MIL	PY
screen	en	Screen	The drawing area that the game sets up (size, colour, title) and on which the snake is shown.	BC, SA, PP, MIL	PY
snake	en	Snake	The creature the player steers, made of segments.	BC, SA, PP, MIL	PY
segment	en	Turtle	One white square of the snake.	BC, SA, PP, MIL	PY
head	en	head	The first segment, which leads the snake and is turned by the arrow keys.	BC, SA, PP, MIL	PY
tail	en	segments[1:]	Every segment behind the head; the game is over when the head touches one of them.	BC, SA, PP, MIL	PY
body	en	segments	All segments of the snake, the head included, in order, the head first.	BC, SA, PP, MIL	PY
starting position	en	STARTING_POSITIONS	One of the three places at which a segment is drawn when the game starts.	BC, MIL	PY
move	en	move	One pass in which each segment takes the place of the one before it and the head goes forward by the move distance.	BC, SA, PP, MIL	PY
move distance	en	MOVE_DISTANCE	How far the head goes in one move, 20 pixels.	BC, MIL	PY
direction	en	heading	The way the head points: up, down, left or right.	BC, SA, PP, MIL	PY
reversal	en	opposite heading	A turn by 180 degrees, so that the head would run into the segment behind it.	BC, SA, PP, MIL	PY
arrow key	en	key name "Up", "Down", "Left", "Right"	One of the four keys with which the player turns the head.	BC, SA, PP, MIL	PY
key binding	en	onkey	The link between an arrow key and the method that turns the head.	BC, PP, MIL	PY
animation loop	en	while game_is_on loop	The loop that refreshes the screen, waits and makes one move, again and again.	BC, PP, MIL	PY
refresh delay	en	REFRESH_DELAY_SECONDS	The wait between two moves, 0.1 seconds.	BC, MIL	PY
food	en	Food	The small blue circle that the snake eats; it is shown at a random place.	BC, SA, PP, MIL	PY
refresh	en	refresh	The food moves to a new random place; it happens when the game starts and every time the food is eaten.	BC, SA, MIL	PY
eat	en	FOOD_COLLISION_DISTANCE	The head comes closer to the food than this distance, which makes the snake grow and the score rise.	BC, MIL	PY
grow	en	extend	The snake gets one more segment, at the place where its last segment is.	BC, SA, MIL	PY
score	en	score	The number of foods the snake has eaten in this game.	BC, SA, PP, MIL	PY
scoreboard	en	Scoreboard	The text at the top of the screen that shows the score.	BC, SA, MIL	PY
wall	en	WALL_LIMIT	The line on every side of the playing field, 280 pixels from the centre; the head must stay inside it and the food is shown inside it.	BC, SA, PP, MIL	PY
touch	en	TAIL_COLLISION_DISTANCE	The head comes closer to a segment of the tail than this distance.	BC, MIL	PY
game over	en	game_over	The end of the game, shown with the text GAME OVER, when the head passes the wall or touches the tail.	BC, SA, PP, MIL	PY
inheritance	en	subclass of Turtle	A class takes over the attributes and methods of another class; Food and Scoreboard take over those of Turtle.	BC, SA, MIL	PY

Rules

• The Business Case, Stakeholder Analysis, Project Plan and milestones use the PO term; the source code and its tests use the IT term. The other design artifacts (Domain Model, Operation Contract, Sequence Diagram, Design Class Diagram, ERD) do not exist in this project.
• One IT term per PO term and one PO term per IT term; no synonyms.
• The planning documents use British spelling (colour, centre); identifiers such as color follow the turtle module and the lectures.
• A code identifier written in backticks in a planning document is an IT term and is allowed there.
• "Step" is not a PO term of the game. In the planning documents it means a step of the project (a task, a milestone), never a move of the snake.
• "Base" is not a PO term of the game. In the planning documents it means the finished main of the day-20 repository that this project adopts, never a part of the game.

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