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Understand anything with visual, interactive courses
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Turn your own docs, slides, or outlines into interactive lessons
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Personalized practice in every lesson.

Fenzo generates custom courses in seconds around your topic and goals. Interactive exercises help make concepts actually stick.

Understand the chain, not just the timeline.

Explore how one event leads to another with interactive timelines that reveal causes, consequences, and turning points.

The First Information Age

144014531470s151715431687inspiredenabledacceleratedenabledprovokedPrinting PressFall of ConstantinopleMass LiteracyReformationScientific RevolutionEnlightenment
SelectedCauseEffect→ direction of cause

Printing Press

1440

Gutenberg's movable-type press cut the cost of books by an order of magnitude — turning text from a scarce.

What caused it
Fall of Constantinopleinspired
What it led to
Mass LiteracyenabledReformationaccelerated

Reformation

1517

Luther's 95 Theses spread through Europe within weeks via the press, permanently fracturing the Catholic Church's authority.

What caused it
Printing PressacceleratedMass Literacyenabled
What it led to
Enlightenmentprovoked

Follow code as it actually runs.

Fenzo walks through each line, showing variables, return values, and the call stack so learners can understand execution instead of guessing.

Tracing Recursive Factorial

1def factorial(n):
2 if n <= 1:
3 return 1
4 result = n * factorial(n - 1)
5 return result
6 
7print(factorial(3))

Return Value

26Returned

Variables

n=23changed
result=26changed

Call Stack

▸factorial(2)
▸·factorial(3)factorial(3)
·<module>
Step 131415 of 15

See how priorities change the answer.

Adjust criteria weights and watch the ranking update, so learners understand why different choices fit different goals.

Database Scorecard

Adjust the weight of each criterion to see how your priorities change the ranking.

OptionSpeed×34Scalability×3Ease×2Cost×3Community×4Total
MongoDB89788121129
PostgreSQL78879118125
Redis106787114124
SQLite739106102109
How much does each criterion matter?0 = ignore · 5 = critical0 = ignore · 5 = critical
Speed3 / 54 / 5
IgnoreCritical
Scalability3 / 5
IgnoreCritical
Ease of use2 / 5
IgnoreCritical
Cost3 / 5
IgnoreCritical
Community4 / 5
IgnoreCritical

Rank summary

MongoDB ranks first with 121129

Strongest weighted contribution: Community (8 × 4 = 32). Ahead of PostgreSQL by 34.

See how programs use memory.

Visualize stack and heap changes step by step, so learners can understand how variables, references, and objects live in memory.

Memory Allocation Visualizer

1x = 42
2name = "Alice"
3scores = [95, 87, 100]
4user = {"name": name, "scores": scores}
5y = x + 1

Memory

Stack

x424B

Heap

Empty

Line 1: The integer 42 is stored directly on the stack as a primitive value.

Step 1 of 5

Turn equations into visual insight.

Plot functions side by side and see how different equations create different shapes, patterns, and behaviors.

Graphing Function Plotter

Equations
f₁(x) =sin(x)sin(x) -sin(x) - 2
f₂(x) =x^2x^2 /x^2 / 4
Variables

Reference a letter (like a or k) in an equation to add it here.

XY−8−448-4-224
Cursor
x2.41
y0.64

Head or Tails in action!

Run repeated coin flips and see how unpredictable outcomes become more stable over time.

The Law of Large Numbers: Coin Flips

Run coin flips or dice rolls to compare theoretical probability with experimental probability. As the number of trials increases, observe whether the experimental results move closer to the expected probabilities.

H
T
0121262
Trials
Heads011732
0.0%100.0%50.0%58.3%51.6%
50.0%
Tails001530
0.0%0.0%50.0%41.7%48.4%
50.0%
ExperimentalTheoretical
Full history(0)(1)(2)(12)(62)

Learn why the order matters.

Arrange steps, test your understanding, and see how each action leads to the next.

Order the Steps: A Perfect Cup of Tea

☕
Goal

Make a perfect cup of tea

🥛Add milk or lemon to taste
🍵Place tea bag in cup
⏱️Steep for 3–5 minutes
💧Pour hot water over the bag
🫖Boil water to 90°C

Watch randomness become predictable.

Roll the dice, run more trials, and see how experimental results move closer to theoretical probability over time.

The Law of Large Numbers: Dice Rolls

Run coin flips or dice rolls to compare theoretical probability with experimental probability. As the number of trials increases, observe whether the experimental results move closer to the expected probabilities.

0121262
Trials
000210
0.0%0.0%0.0%16.7%16.1%
16.7%
000111
0.0%0.0%0.0%8.3%17.7%
16.7%
011311
0.0%100.0%50.0%25.0%17.7%
16.7%
000210
0.0%0.0%0.0%16.7%16.1%
16.7%
001310
0.0%0.0%50.0%25.0%16.1%
16.7%
000110
0.0%0.0%0.0%8.3%16.1%
16.7%
ExperimentalTheoretical
Full history(0)(1)(2)(12)(62)