Built for how you learn best

Pro

Understand anything with visual, interactive courses

Create custom courses from any topic, goal, or question

Turn your own docs, slides, or outlines into interactive lessons

Learn deeply with rich visuals, simulations, and practice exercises

On-demand AI mentor to explain complex concepts and guide you

Book Summaries NEW — generate and browse a full library

Track your progress and close learning gaps

Share your courses with classmates, teammates, or friends

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Product Hunt credit

Everything in Pro, with more power and priority

Our most capable AI model, for sharper explanations and courses

Higher AI mentor quota, with priority responses

Cross-course knowledge graph and adaptive course generation

Share with twice as many people as Pro

COMING SOON

•Fenzo Paths, guided multi-course journeys

•AI Role Play, practice concepts in live scenarios

Stripe

Acceptable Use Policy

applies

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

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))

See how priorities change the answer.

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

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

Option	Speed×34	Scalability×3	Ease×2	Cost×3	Community×4	Total
MongoDB	8	9	7	8	8	121129
PostgreSQL	7	8	8	7	9	118125
Redis	10	6	7	8	7	114124
SQLite	7	3	9	10	6	102109

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

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

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

Head or Tails in action!

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

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

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)

Watch randomness become predictable.

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

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)

Built for how you learn best

Personalized practice in every lesson.

Understand the chain, not just the timeline.

The First Information Age

Printing Press

Reformation

Follow code as it actually runs.

Tracing Recursive Factorial

See how priorities change the answer.

Database Scorecard

See how programs use memory.

Memory Allocation Visualizer

Turn equations into visual insight.

Graphing Function Plotter

Head or Tails in action!

The Law of Large Numbers: Coin Flips

Learn why the order matters.

Order the Steps: A Perfect Cup of Tea

Make a perfect cup of tea

Watch randomness become predictable.

The Law of Large Numbers: Dice Rolls