021-snake-game/docs/milestones/mil-003-check-against-day-21.md

MIL-003: Check against day 21

Metadata

Key	Value
ID	MIL-003
CrossReference	BC-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-006 (Go)	f13d004

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Purpose

This gate decides whether the adopted game does what the five day-21 lectures say, and whether the repository is finished. The base was written against assumed day-21 numbers; this milestone replaces the assumptions by the values of the lecture summaries, corrects the code where it differs, and finishes the README. It is the last gate of PP-001. The work is delivered on the branch mil-003-check-against-day-21 and one pull request.

Deliverable

A comparison table in the pull request with one row per lecture point below (value in the lecture summary, value in the code, same or different), the corrections of every difference with tests, a finished README.md that describes the whole game and this repository, and a check of the repository page. If nothing differs, the table says so and no source file changes.

The lecture points are the specification of this milestone:

Lecture	Point of the lecture summary	Where it lives in the code
1. Inheritance and slicing	One class inherits the attributes and methods of another; lists are sliced	class Food(Turtle), class Scoreboard(Turtle), segments[1:]
2. Detect collisions with food	Food inherits from Turtle; a blue circle of 10 by 10 pixels	FOOD_SHAPE, FOOD_COLOR, FOOD_SIZE (0.5 of a default turtle)
2. Detect collisions with food	The random place comes from the random module and is never at the edge of the screen	random_coordinate, WALL_LIMIT (280)
2. Detect collisions with food	The snake eats the food when the distance between the head and the food is less than 15 pixels	FOOD_COLLISION_DISTANCE, eat_food_if_close
2. Detect collisions with food	refresh gives the food new random coordinates; it runs when the food is made and at every collision	Food.refresh, called from Food.__init__ and eat_food_if_close
3. Scoreboard	Scoreboard inherits from Turtle; the score starts at 0; the text is written with alignment and font; the turtle is hidden; colour and place are set	Scoreboard.__init__, SCOREBOARD_COLOR, SCOREBOARD_POSITION, SCOREBOARD_ALIGNMENT, SCOREBOARD_FONT
3. Scoreboard	increase_score adds 1; the old text is cleared before the new text is written; update_scoreboard does both; alignment and font are constants	Scoreboard.increase_score, Scoreboard.update_scoreboard
4. Wall	The wall is at 280 and -280 on both axes; passing it stops the game (game_is_on becomes false); GAME OVER is shown in the middle with the score still visible	Snake.hits_wall, WALL_LIMIT, Scoreboard.game_over, GAME_OVER_TEXT, GAME_OVER_POSITION
5. Tail	Eating adds a segment: extend calls add_segment with the position of the last segment	Snake.extend, Snake.add_segment
5. Tail	The head touches the tail when it is closer than 10 pixels to a segment; the head is skipped, so it does not collide with itself	Snake.hits_tail, TAIL_COLLISION_DISTANCE, segments[1:]

Go / No-Go Criteria

#	Criterion (objectively checkable)	Go	No-Go
1	The comparison is complete	The pull request has one row for every lecture point above, with the value of the lecture summary, the value of the code and the result	A lecture point has no row
2	Every difference is resolved	Each row marked different is corrected in the code with a test, or S01 accepts it with a reason written in the pull request	A difference stays open
3	The lessons of day 21 are visible	Food and Scoreboard are subclasses of turtle.Turtle and call super().__init__(); hits_tail loops over segments[1:]	Either class does not inherit from Turtle, or the loop includes the head
4	Food is shown	A manual run shows one small blue circle at a random place inside the wall; a second run shows another place; it is never at the very edge of the screen	No food, not a circle, or outside the wall
5	The snake eats	When the head comes closer than FOOD_COLLISION_DISTANCE the food moves to a new random place, the snake grows by one segment and the score rises by 1; it works again for the next food	Any of the three does not happen, or the score rises without the food being eaten
6	The scoreboard shows the score	White text Score: 0 at the top centre; after eating it shows Score: 1 and the old text is gone	Text overlaps, is missing or is not at the top centre
7	The wall ends the game	A manual run shows the game ending when the head passes the wall on each of the four sides; GAME OVER is in the middle of the window and the score stays visible	The game goes on beyond the wall, ends inside it, or shows no text
8	The tail ends the game	Turning the head into the body ends the game; normal movement, including the moves right after eating, does not	The game does not end, or ends without a touch
9	A click closes the window	After game over a click closes the window and the program ends with exit code 0; closing the window during play also ends with exit code 0 and no traceback	The window stays, or a traceback appears
10	Tests and checks are green	pytest exits 0 with no display; ruff check, ruff format --check and mypy exit 0; doxygen Doxyfile ends with 0 warnings	Any check fails
11	The README is finished	It describes the whole game (moving, food, score, game over, closing) and this repository; it has no placeholder and no sentence that is out of date; a fresh clone reaches a green pytest by following it	A placeholder or an out-of-date sentence, or a command fails
12	The repository page is complete	Description is non-empty and there are at least 5 topics on the git host	Description empty or fewer than 5 topics
13	The game matches the lecture	S01 compares the finished game with the lecture video and notes any difference in the pull request	An undocumented difference
14	The code is reviewed	If a source file changed, RC-* against QC-PY-001 has the verdict Go; if none changed, the pull request says so	Verdict No-Go or Go-with-conditions

Dependencies

Depends on	Reason
MIL-002 accepted and merged	The game that is checked exists there

Traceability

Business Case objective / KPI / user story	Reference
Objectives 2 and 3: food, eating, score, game over as the lectures give them	BC-001, criteria 2 and 3 in Success Criteria
Objective 4: inheritance and slicing	BC-001, criterion 4 in Success Criteria
Objective 1: the day-20 behaviour is kept	BC-001, criterion 1 in Success Criteria
Objective 7: tests without a display	BC-001, criterion 5 in Success Criteria
Objective 8: README and Doxygen	BC-001, criteria 6 and 7 in Success Criteria
Objective 9: traceable steps	BC-001, criterion 10 in Success Criteria
Objective 10: repository page	BC-001, criterion 11 in Success Criteria
Design of any corrected class or method: no Design Class Diagram exists; a correction traces to its lecture point in the table above, a recorded deviation from QC-PY-001 criterion 10 as in MIL-002	PP-001

Ownership

Role	Stakeholder ID (SA)
Owner	S01
Approving reviewer	S01

Target Date

2026-10-14 — last of three gateways, inside the one-week plan of PP-001 that ends 2026-10-16.

Tasks

#	Task	Summary	Needs its own Use Case/User Story?	Reference
1	Check inheritance and slicing against lecture 1	Compare the code with the lecture on class inheritance and slicing: Food and Scoreboard are subclasses of Turtle that call super().__init__(), and the tail check slices the segments so that the head is left out. Write the result as rows of the comparison table in the pull request.	No
2	Check the food against the collision lecture	Compare the food with the lecture on collisions with food: a blue circle of 10 by 10 pixels (FOOD_SIZE 0.5), a random place from the random module that is never at the edge of the screen, refresh at creation and at every collision, and the eating distance of less than 15 pixels. Write the result as rows of the comparison table.	No
3	Check the scoreboard against its lecture	Compare the scoreboard with the lecture: the score starts at 0, the text is written with alignment and font taken from constants, the turtle is hidden, increase_score adds 1, and update_scoreboard clears the old text before it writes the new one. Write the result as rows of the comparison table.	No
4	Check the wall and the game-over text against their lecture	Compare the wall and the end of the game with the lecture: the wall is at 280 and -280 on both axes, passing it sets game_is_on to false, and GAME OVER is shown in the middle with the score still visible. Write the result as rows of the comparison table.	No
5	Check growth and the tail against their lecture	Compare extend, add_segment and the tail check with the lecture: extend adds a segment at the position of the last segment, and the head touches the tail below 10 pixels with the head itself skipped. Write the result as rows of the comparison table.	No
6	Correct the code where it differs from the lectures	For every row of the comparison table marked different, change the constant or the code, add or change the test that proves it, and say so in the pull request. If no row differs, change no source file and state that in the pull request.	No
7	Finish the README for the Day 21 repository	Rewrite the Status and Run sections of README.md for the whole game (moving, food, score, game over, closing), remove every sentence that is out of date, update the Project layout, and confirm that doxygen Doxyfile ends with 0 warnings and that a fresh clone reaches a green pytest by following the README.	No
8	Check the repository page and compare with the video	Check on the git host that the description and at least 5 topics are still set, run the finished game next to the lecture video, and write every difference in the pull request.	No

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