Python · JavaScript · nothing to install

Learn to code,
one bit at a time

Short lessons, real challenges and a profile that climbs the ranks like the industry does: from Student to Principal.

72: lessons written
33: challenges with tests
8: career ranks

How you learn

You do not read code. You write it.

Every lesson is 8 to 12 exercises of five minutes each. The code really runs inside the app: if your answer produces the right result, it is right.

Predict the output

print("Hola")

print("mundo")

Hola mundo

You read the program and say what it prints, before running it.

Put the code in order

edad = 20

if edad >= 18:

print("Puedes votar")

print("Todavía no")

Drag the lines around until the program does what the exercise asks for.

Find the bug

def promedio(a, b):

return a + b / 2

print(promedio(8, 10))

Line 2

The division happens before the addition. It needs parentheses: (a + b) / 2

You also practise withfill in the blankmatch the pairswrite the unit project

Uptime

One day at a time. No punishment.

Uptime counts the days in a row you keep the service up. If one day you cannot, a hotfix covers it. There are no lives and no hearts to lose here: the question you get wrong simply comes back.

2 hotfixes savedDaily of 50 XP

12days of uptimeyour best streak: 21today: up

Activity

last 24 weeks

Challenges

Real challenges, with real tests.

33 katas in Python and JavaScript. You write the function in the editor, you run the tests, and they pass or they do not. Behaviour is what gets graded, not the text: if your solution gives the right result, it is right.

O(1)
O(log n)
O(n)
O(n log n)
O(n²)
O(2ⁿ)

pybusqueda_binaria.pyO(log n)

def binary_search(nums, value):

lo, hi = 0, len(nums) - 1

while lo <= hi:

mid = (lo + hi) // 2

if nums[mid] == value:

return mid

if nums[mid] < value:

lo = mid + 1

else:

hi = mid - 1

return -1

Tests

4 / 40.42 s

It finds it in the middle
Not in the list: -1
An empty list
Hidden test: A thousand numbers

Career

From Student to Principal.

Your profile climbs the ranks with XP, solved challenges and a technical interview at every step. The same eight names you will meet at work.

0Estudiante
300Becario
1,500you are hereJunior
5,000Semi Senior
12,000Senior
25,000Tech Lead
45,000Staff
75,000Principal

Technical interview

From Junior on, every promotion is earned by answering questions about code, not by piling up points.

Challenges by difficulty

Semi Senior asks for 10 challenges at O(n) or harder. Senior asks for O(n log n).

A whole course

Tech Lead means finishing every unit of one language, projects included.

Hi! I am Nube. I will be with you all the way to Principal.

Nube shows up when it matters: when you get it right, when you are stuck, while the interpreter is loading and when you have not opened the app in days. Not as decoration in every corner, and never to tell you off.

no livesno punishmentwrong answers come back

Start today

Your first lesson takes five minutes.

Python and JavaScript run inside the app, with nothing to install on your computer. No ads inside.

Get it for iPhone Get it for Android

The app reaches the stores soon. These links go live that day.

Learn to code,one bit at a time