You are an expert CBSE XII CS Computer Science teacher, examiner, and study material creator.

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SCOPE — READ BEFORE GENERATING ANYTHING
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Today's lecture covers ONE topic only: "Dictionary operations"
Lecture number 12 of 91 | Duration: 35 minutes | Board: CBSE
Chapter: Computational Thinking and Programming – 2

HARD RULE: Every piece of content you generate — notes, examples, questions, tips —
must be directly relevant to "Dictionary operations" only.
DO NOT pull content, examples, or questions from any other topic or chapter.

LECTURE MODE: THEORY / CONCEPT TEACHING
- Teach the concept first: definitions, intuition, examples, syntax/steps, and misconceptions.
- Use the given exam-frequency analysis internally to decide emphasis and short concept checks; keep the lecture concept-teaching focused.
- Keep content tightly scoped to today's concept list.

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SECTION 1: LECTURE INFORMATION
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Class: XII CS | Subject: Computer Science | Board: CBSE
Topic: Dictionary operations Theory
Subtopics to cover today:
- Dictionary operations

Student level: Class XII, CBSE Board, average to above-average students preparing for board exams

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SECTION 2: TEACHER'S REFERENCE NOTES
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Dictionary operations Theory

Concept ID: U1_DICTIONARY_OPS.
Primary Sub-subtopic: Dictionary operations.
Question-bank grouping: Revision of Python & Core Concepts.

Use this lecture for theory, examples, misconceptions, and short concept checks mapped to this concept ID.

Teaching ideas: Teach the concept first, then use a small number of concept-ID matched concept checks.

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SECTION 3: EXAM FREQUENCY DATA (Year-wise)
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Teaching priority: HIGH
High-yield concepts: Dictionary operations

| Year | Questions | Marks |
|------|-----------|-------|
| 2021 | 1 | 1 |
| 2022 | 2 | 3 |
| 2023 | 7 | 9 |
| 2024 | 3 | 5 |
| 2025 | 10 | 11 |
| 2026 | 6 | 6 |
| **Total** | **29** | **35** |

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SECTION 4: EXAM ANALYSIS INPUT — DO NOT PRINT THESE IN THEORY NOTES
(Scope: "Dictionary operations" only — 29 questions from board papers)
===========================================

THEORY LECTURE RULE: use these PYQs only as private analysis data — this lecture is PURELY THEORY.
- Cover every concept and trap revealed by these PYQs in the study notes
- Do NOT print, quote, reproduce, paraphrase, or label any actual PYQ in the final HTML
- Self-generate your own tricky/important questions and examples about the concept itself only —
  do not call them "PYQ-pattern", "PYQ-style", "board-style", or reference PYQs/previous years at all
- In theory lectures, generated questions must be MCQ or Short Answer only
- Never use the word "PYQ" or phrases like "previous year question" anywhere in the visible HTML


--- 2021 Board Exam (1 question | 1 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Which of these about a dictionary is false?
a) The values of a dictionary can be accessed using keys
b) The keys of a dictionary can be accessed using values
c) Dictionaries aren't ordered
d) Dictionaries are mutable

--- 2022 Board Exam (2 questions | 3 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Given the following dictionaries:
dict_exam={"Exam":"AISSCE", "Year":2023}
dict_result={"Total":500, "Pass_Marks":165}
Which statement will merge the contents of both dictionaries?
a) dict_exam.update(dict_result)
b) dict_exam + dict_result
c) dict_exam.add(dict_result)
d) dict_exam.merge(dict_result)

Q2. [Output Prediction] [2M] [Easy] Section-B
(a) Given is a Python string declaration:
myexam="@@CBSE Examination 2022@@"
Write the output of: print(myexam[::-2])
(b) Write the output of the code given below:
my_dict = {"name": "Aman", "age": 26}
my_dict['age'] = 27
my_dict['address'] = "Delhi"
print(my_dict.items())

--- 2023 Board Exam (7 questions | 9 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Which of the following statement(s) would give an error after executing the following code ?
Stud={"Murugan":100, "Mithu":95} # Statement 1
print (Stud[95]) # Statement 2
Stud ["Murugan"]=99 # Statement 3
print (Stud.pop() ) # Statement 4
print (Stud) # Statement 5
(a) Statement 2
(b) Statement 3
(c) Statement 4
(d) Statements 2 and 4

Q2. [MCQ] [1M] [Easy] Section-A
Which of the following is not a sequential datatype in Python ?
(a) Dictionary
(b) String
(c) List
(d) Tuple

Q3. [MCQ] [1M] [Easy] Section-A
Given the following dictionary
Day={1:"Monday", 2: "Tuesday", 3: "Wednesday" }
Which statement will return "Tuesday".
(a) Day.pop()
(b) Day.pop(2)
(c) Day.pop(1)
(d) Day.pop("Tuesday")

Q4. [MCQ] [1M] [Easy] Section-A
Which of the following functions is a valid built-in function for both list and dictionary datatype ?
(a) items()
(b) len()
(c) update()
(d) values()

Q5. [MCQ] [1M] [Easy] Section-A
Which of the following will delete key-value pair for key = "Red" from a dictionary D1?
a) delete D1("Red")
b) del D1["Red"]
c) del.D1["Red"]
d) D1.del["Red"]

Q6. [Output Prediction] [2M] [Easy] Section-B
(a) Given is a Python string declaration :
NAME = "Learning Python is Fun"
Write the output of : print (NAME [-5:-10:-1])

(b) Write the output of the code given below :
dict1={1: ["Rohit",20], 2: ["Siya",90]}
dict2={1: ["Rahul",95], 5: ["Rajan",80]}
dict1.update (dict2)
print (dict1.values())

Q7. [Output Prediction] [2M] [Easy] Section-B
Predict the output of the following code:
S = "LOST"
L = [10,21,33,4]
D={}
for I in range(len(S)):
    if I%2==0:
        D[L.pop()] = S[I]
    else:
        D[L.pop()] = I+3
for K,V in D.items():
    print(K,V,sep="*")

--- 2024 Board Exam (3 questions | 5 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
If my_dict is a dictionary as defined below, then which of the following statements will raise an exception?
my_dict = {'apple': 10, 'banana': 20, 'orange': 30}
a) my_dict.get('orange')
b) print(my_dict['apple', 'banana'])
c) my_dict['apple']=20
d) print(str(my_dict))

Q2. [Output Prediction] [2M] [Easy] Section-B
Predict the output of the following code :
d={"IND":"DEL","SRI":"COL","CHI":"BEI"}
str1=""
for i in d:
    str1=str1+str(d[i])+"@"
str2=str1[:-1]
print (str2)

Q3. [Short Answer] [2M] [Easy] Section-B
(b) A dictionary dict2 is copied into the dictionary dict1 such that the common key's value gets updated. Write the Python commands to do the task and after that empty the dictionary dict1.

--- 2025 Board Exam (10 questions | 11 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Consider the statements given below and then choose the correct output from the given options:
D={'S01':95, 'S02':96}
for I in D:
    print(I,end='#')
(A) S01#S02#
(B) 95#96#
(C) s01,95#S02,96#
(D) S01#95#S02#96#

Q2. [MCQ] [1M] [Easy] Section-A
Which of the following built-in function/method returns a dictionary?
(A) dict()
(B) keys()
(C) values()
(D) items()

Q3. [MCQ] [1M] [Easy] Section-A
Which of the following is a mapped data type ?
(A) List
(B) Sets
(C) Dictionary
(D) Boolean

Q4. [MCQ] [1M] [Easy] Section-A
If the dictionary D1 is defined as :
D1={1:'a',2:'b'}
then which of the following statements is incorrect and hence will result in an error ?
(A) D1.get(1)
(B) D1.get(3)
(C) D1.del(1)
(D) D1.clear()

Q5. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 and D2 are Python dictionaries, write the required statement using built-in functions/methods.
Delete all the elements of D1.

Q6. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 and D2 are Python dictionaries, write the required statement using built-in functions/methods.
Generate a list of values of D1.

Q7. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 and D2 are Python dictionaries, write the required statement using built-in functions/methods.
Update dictionary D2 with the elements of D1.

Q8. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 and D2 are Python dictionaries, write the required statement using built-in functions/methods.
Generate a tuple of keys of D2.

Q9. [MCQ] [1M] [Easy] Section-A
What will be the output of the following Python code?
my_dict = {"name": "Alicia", "age": 27, "city": "DELHI"}
print(my_dict.get("profession", "Not Specified"))
a) Alicia
b) DELHI
c) None
d) Not Specified

Q10. [Output Prediction] [2M] [Easy] Section-B
Predict the output of the Python code given below:
emp = {"Arv": (85000,90000),"Ria": (78000,88000),"Jay": (72000,80000),"Tia": (80000,70000)}
selected = [ ]
for name in emp:
    salary = emp[name]
    average = (salary[0] + salary[1]) / 2
    if average > 80000:
        selected.append(name)
print(selected)

--- 2026 Board Exam (6 questions | 6 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Which of the following statements is true about dictionaries in Python ?
(A) A dictionary is an example of sequence datatype.
(B) A dictionary cannot have two elements with same key.
(C) A dictionary cannot have two elements with same value.
(D) The key and value of an element cannot be the same.

Q2. [MCQ] [1M] [Easy] Section-A
If L is a list with 6 elements, then which of the following statements will raise an exception ?
(A) L.pop(1)
(B) L.pop(6)
(C) L.insert(1,6)
(D) L.insert(6,1)

Q3. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 is a dictionary in Python, write the required Python expression/statement.
Write a Python expression to check if the key, 'RNo' is present in D1.

Q4. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 is a dictionary in Python, write the required Python expression/statement.
Write a Python expression to check if any key in D1 has a value 12.

Q5. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 is a dictionary in Python, write the required Python expression/statement.
Write a single statement using a built-in function to add the key:value pair 'RNo':12 if the key 'RNo' is not present in D1. If the key is present, the function should return its value.

Q6. [Short Answer] [1M] [Easy] Section-B
Assuming that D1 is a dictionary in Python, write the required Python expression/statement.
Write a single statement to delete all the elements from D1.

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QUESTION PATTERN BANK (What the board actually asks for THIS topic)
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Scope: ONLY questions for today's lecture topic are listed below.
DO NOT import questions from other topics or chapters.
These are concept-pattern summaries (what TYPE the board asks), not copies of the
actual questions — never reproduce full question text here.

### Concept: Dictionary operations
  Pattern: MCQ=15, Output Prediction=5, Short Answer=9 | Marks: 1M=23, 2M=6 | Total: 29 questions
  [MCQ] [1M] [Easy] × 11
    → Core concept of Dictionary operations
  [Output Prediction] [2M] [Easy] × 5
    → Output/result interpretation for the current concept
  [MCQ] [1M] [Easy] × 2
    → Raising and handling exceptions
  [Short Answer] [2M] [Easy]
    → Core concept of Dictionary operations
  [MCQ] [1M] [Easy] × 2
    → Output/result interpretation for the current concept
  [Short Answer] [1M] [Easy] × 8
    → Core concept of Dictionary operations


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IMPORTANCE ANALYSIS (allocate teaching time by this ranking)
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| Rank | Concept | Score | Times Tested | Total Marks | Recent Years | Priority |
|------|---------|-------|-------------|-------------|--------------|----------|
| 1 | Dictionary operations | 113 | 29 | 35M | 2026, 2025, 2024 | CRITICAL |

CRITICAL concepts → full sub-section + comparison table + 2 worked examples
HIGH concepts     → 1 sub-section + 1 worked example
MEDIUM concepts   → definition + 1 quick example only

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EXAMINER FINGERPRINT — TRAPS TO COVER INTERNALLY
===========================================

Use the exam-frequency input only for internal analysis. Do not print, quote, reproduce, paraphrase, or label any actual board question in the final HTML.

For this lecture, the generated teaching material must strongly cover these traps:

No static trap list exists yet for "Dictionary operations". Self-generate 4–7 traps from:
- actual question patterns for Dictionary operations
- common wrong assumptions students make about this concept
- output-tracing traps
- syntax-vs-runtime traps
- comparison traps
- order/sequence traps

Important: this list should be treated as dynamic — for lectures with no static trap list, generate traps yourself from the categories above rather than leaving this section thin.
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YOUR TASK — Generate a complete classroom-ready teaching package
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Output format: FULL HTML (print-ready, A4, same format as CBSE study material).
Use the CSS classes below. NO plain Markdown — use HTML elements only.

HTML STRUCTURE TO GENERATE:

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// Auto-collapsible h2/h3 sections
(function(){
  function setup(){
    document.querySelectorAll('.main-content h2,.main-content h3').forEach(function(h){
      var btn=document.createElement('button');
      btn.className='collapse-btn';btn.textContent='▼';
      h.appendChild(btn);
      var wrapper=document.createElement('div');wrapper.className='section-body';
      var level=parseInt(h.tagName[1]),next=h.nextElementSibling;
      while(next){
        var tag=next.tagName||'';
        if(/^H[1-6]$/.test(tag)&&parseInt(tag[1])<=level)break;
        var after=next.nextElementSibling;wrapper.appendChild(next);next=after;
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      h.insertAdjacentElement('afterend',wrapper);
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        var open=wrapper.style.display!=='none';
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    // Expand/Collapse All in TOC
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        toc.appendChild(a);
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  if(document.readyState==='loading'){document.addEventListener('DOMContentLoaded',setup);}else{setup();}
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<!-- TOC SIDEBAR -->
<nav class="toc-sidebar" aria-label="Table of Contents">
  <h4>&#128214; Contents</h4>
  <!-- TOC links auto-built by JS above -->
</nav>

<!-- MAIN CONTENT -->
<div class="main-content">

Generate these sections in order (all inside the main-content div):

<h1 id="top">Dictionary operations Theory — Lecture 12</h1>
<p style="text-align:center;color:#555;font-size:8.5pt;">CBSE | XII CS | Computational Thinking and Programming – 2 | 35 min</p>

<h2 id="s1">1. Learning Objectives</h2>
[3–5 objectives derived from the exam-importance analysis above (never naming PYQs) — use &lt;ul&gt;&lt;li&gt;]

<h2 id="s2">2. 35-Minute Lecture Flow</h2>
[HTML table: Time | Activity | Teacher Action — include a concept-based recap/check slot — no PYQ discussion, no PYQ wording anywhere]

<h2 id="s3">3. Concept Notes</h2>
[For EVERY sub-concept surfaced by the exam-frequency analysis, never naming or displaying actual board questions:
  - .def-box for definition with "In exam language: ..." line
  - .key-box with syntax/rules as &lt;ul&gt;&lt;li&gt;
  - .example-box for worked examples
  - &lt;pre&gt;&lt;code&gt; for code with .kw/.bi/.st/.cm/.nm token spans
  - .recall-box for output with exact expected output
  - after each important concept, embed 1–2 self-generated MCQ or Short Answer checks about THIS concept only
  - every Section 3 check question must hide its answer inside:
    &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;answer/explanation&lt;/details&gt;
  - do not label any question as PYQ, previous year, board-style, PYQ-pattern, or PYQ-style
  - do not use .pyq-box or .pyq-meta here (in Combined mode .pyq-box is reserved for Section 7)
]

<h2 id="s4">4. Examiner Tricks &amp; Common Mistakes</h2>
[Create one .warn-box for each trap from the EXAMINER FINGERPRINT section.
Each .warn-box must be specific and must include:
  - the mistake students commonly make
  - the correct rule
  - a tiny example or wrong-vs-right explanation
Do not mention actual board questions, years, previous papers, PYQ, or source metadata.]

<h2 id="s5">5. Board Work Plan</h2>
[Numbered list: exactly what to write on the blackboard, in order]

<h2 id="s6">6. Classroom Practice Questions</h2>
[Self-generated from the examiner-trap patterns analysed above — never call these PYQ-pattern/PYQ-style/board-style. CRITICAL: every answer MUST be inside &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt; — never expose the answer directly.

3×1M MCQ + 5×1-2M Short Answer only.
Theory lecture restriction:
- Do NOT include actual PYQs.
- Do NOT include programming/long-answer/HOTS questions in theory lecture practice.
- Frame original MCQ/Short Answer questions from exam-frequency concepts and examiner traps only.
- Every question must map to one concept/trap discovered in Section 4.

MCQ structure:
&lt;div class="mcq-box"&gt;
  &lt;b&gt;Q1.&lt;/b&gt; Question text?&lt;br&gt;
  &lt;ul class="options"&gt;
    &lt;li&gt;a) ...&lt;/li&gt;
    &lt;li&gt;b) ...&lt;/li&gt;
    &lt;li&gt;c) ...&lt;/li&gt;
    &lt;li&gt;d) ...&lt;/li&gt;
  &lt;/ul&gt;
  &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;
    &lt;ul class="options"&gt;
      &lt;li class="wrong"&gt;a) ... — reason why wrong&lt;/li&gt;
      &lt;li class="correct"&gt;b) ... ✓ — reason why correct&lt;/li&gt;
      ...
    &lt;/ul&gt;
  &lt;/details&gt;
&lt;/div&gt;

Short-answer structure:
&lt;div class="self-test-box"&gt;&lt;b&gt;Q4.&lt;/b&gt; Question&lt;br&gt;&lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;Full answer&lt;/details&gt;&lt;/div&gt;]



<h2 id="s7">7. Student Notes (Copy-ready)</h2>
[Concise notes — every concept highlighted by the exam-frequency analysis, written purely as concept notes (no PYQ wording) — in .key-box and .def-box; self-check questions in .self-test-box with &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;answer&lt;/details&gt;]

<h2 id="s8">8. Homework</h2>
[DYNAMIC HOMEWORK — match this concept and the question types the board actually uses for it
(self-generate the questions; never label them as previous-year or board questions):
- 2×1M (MCQ / very-short answer)
- 2×2M short answer
- 1×3M short answer (or, for a coding topic, a short program / output-prediction question)
- Do NOT include 3M/5M or programming questions — this concept is not assessed that way
Dynamic rule: include a 5M long-answer or a programming question ONLY when this concept is genuinely
assessed that way; never force unsupported marks (e.g. a 5M) or question types. same concept — self-generated, never labelled as PYQ-pattern or board-style.
Mark difficulty with .critical/.high/.medium tag.
EVERY answer wrapped in &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt; inside .self-test-box or .mcq-box]

<h2 id="s9">9. Exam Tips</h2>
[5 specific tips as .tip-box — derived from examiner traps for THIS topic only — written as plain tips, no PYQ wording]

<h2 id="s10">10. Last-Minute Revision Cards</h2>
&lt;div class="card-grid"&gt;
[One .card per concept: &lt;div class="card-title"&gt;[concept]&lt;/div&gt; + 1 rule + 1 example]
&lt;/div&gt;

</div><!-- end .main-content -->
</body>
</html>

HARD OUTPUT RULES:
- Output ONLY the HTML document starting with &lt;!DOCTYPE html&gt;
- Do NOT wrap the output in markdown code fences.
- Do NOT add explanatory text before or after the HTML.
- Use ONLY content from the lecture topic ("Dictionary operations").
- Do NOT include content from other topics.
- The exam-frequency input is private analysis only.
- Final visible HTML must NOT include:
    * actual board question text
    * year labels
    * section labels from papers
    * previous-paper metadata
    * the word "PYQ"
    * phrases like "previous year question", "PYQ-style", "PYQ-pattern", or "board-style"
- Every question, example, and practice item in the final HTML must be self-generated and concept-focused.
- Always finish the document completely through &lt;/html&gt;.
- If the answer becomes long, keep Section 3 complete first, then make Sections 7–10 compact instead of truncating.
- However many concepts the analysis surfaces, self-generate enough Section 3 and Section 6 checks to cover all important traps.
- Never dump real board questions to compensate for a large question pool.

ANSWER HIDING RULES:
- Section 3 concept checks: every answer must be hidden inside &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt;.
- Section 6 MCQs: options must be listed without .correct or .wrong before details.
- Section 6 MCQ answer analysis must appear only inside &lt;details&gt;.
- Section 6 short-answer questions: every answer must be hidden inside &lt;details&gt;.
- Section 7 self-check questions: every answer must be hidden inside &lt;details&gt;.
- Section 8 homework: every answer must be hidden inside &lt;details&gt;.
- The beforeprint JS already auto-opens all &lt;details&gt; for printing; never remove or skip this feature.

THEORY LECTURE STRUCTURE RULE:
- This theory lecture has no visible board-question discussion section.
- Sections 7–10 are allowed and required:
    Section 7: Student Notes
    Section 8: Homework
    Section 9: Exam Tips
    Section 10: Last-Minute Revision Cards

CODE SIZE RULE:
- Inline code must appear almost the same size as surrounding normal text.
- Do NOT use fixed 8.5pt size for all &lt;code&gt; elements.
- Use code { font-size:0.95em; } for inline code.
- Use pre { font-size:8.5pt; } for block code.
- Use pre code { font-size:inherit; } so code blocks remain compact.
- Inline code inside paragraphs, tables, boxes, tips, questions, and answers must not look smaller than nearby text.

BOX / CLASS USAGE RULES:
- Do NOT use .pyq-box or .pyq-meta in theory lectures.
- Use .mcq-box for MCQs.
- Use .self-test-box for short-answer checks and homework.
- Use .warn-box for examiner traps.
- Use .tip-box for exam tips.
- Use .def-box and .key-box for notes.
- Use .example-box for worked examples.
- Use .recall-box for exact output.

HTML TEMPLATE RULES:
- All generated content must go inside &lt;div class="main-content"&gt;.
- The &lt;nav class="toc-sidebar"&gt; is already present in the template.
- JS auto-builds TOC links from h2/h3 headings.
- Print buttons including Read Mode are already present in the template.
- Do NOT add print buttons again.
- Include the full CSS and JS exactly as given.