Daily Coding Challenges & Projects

Frontend Mini Project Challenge

CSS Animation Effects

Challenge :

Create a Neon Text Flicker Animation using only CSS

Requirements :

• Use @keyframes and text-shadow to simulate flickering.
• Add color transitions and glow effect.

Bonus : Make it reusable using CSS variables.

Backend Challenge

Java/Kotlin

Challenge : Implement a Rate Limiter in Java or Kotlin

Goal : Build a class that allows a maximum number of requests per time window (e.g., 5 requests every 10 seconds).

Bonus : Use a sliding window or token bucket approach.

Database Query Challenge

Problems on SQL - HR Database :

1. Write a SQL query to retrieve the names and hire dates of the top 5 most recently hired employees in each department.
2. Write a SQL query to list departments that have more than 5 employees who joined before 2020.

Data Structures & Algorithms Challenge

• Easy:
• Problem : Given an array of integers, return true if any value appears at least twice.
• Hint : Use a Set to track seen values.
• Medium:
• Problem : Find the longest palindromic substring in a given string.
• Hint : Try expanding from the center.
• Hard:
• Problem : You are given n items with weights and values. Maximize the value in a knapsack of capacity W.
• Hint : Use dynamic programming (0/1 knapsack approach).

Bug of the Day

Java/Kotlin

Language : Java Bug

Buggy Code:

public class Counter {
    private int count;

    public void increment() {
        count++;
    }

    public static void main(String[] args) {
        Counter counter = null;
        counter.increment();
    }
}

Challenge : What’s wrong with this code? Fix it and explain why the error occurs.

📋 Daily Micro-Project

Backend Focus :

Project :

Build a simple Notes REST API using Kotlin + Spring Boot

Requirements :

• CRUD endpoints for creating, reading, updating, deleting notes.
• Use in-memory storage like Map.
• Optional: Swagger for API docs.

Trivia: 5 Fun Facts

1. Kotlin was officially announced by JetBrains in what year?
2. Java was initially called “Oak”.
3. The first website ever created was hosted at info.cern.ch
4. CSS3 introduced keyframes for animation – true or false?
5. Java is platform-independent because of the JVM (Java Virtual Machine).

Tool & Resource of the Day

Tool : Spring Initializr

Quickly bootstrap new Spring Boot projects with dependencies.

https://start.spring.io

Resource Roundup

• [Kotlin in Action (Book)]

Interview Question of the Day

Daily Interview Questions

Frontend :
1. What is the difference between position: absolute and position: fixed in CSS?
2. Explain how z-index works in stacking elements.
3. What are pseudo-elements in CSS?
4. How do media queries enable responsive design?

Backend ( Java/Kotlin ) :
1. How is memory managed in Java?
2. What’s the difference between == and .equals() in Java?
3. Explain coroutines in Kotlin and how they differ from Java threads.
4. What is dependency injection and how does Spring implement it?

Database ( SQL ) :
1. How does a foreign key differ from a primary key?
2. What’s the purpose of a subquery?
3. What’s a clustered index?

Others :
1. What is the JVM and how does it work?
2. What is CI/CD and how does it improve software delivery?

Daily Quiz Challenge

Frontend Quiz ( CSS ) :

1. Which CSS property creates animation transitions?
• animation
• transition
• animate
• keyframe
2. What does transform: scale(2) do?
• Shrinks the element
• Doubles the size
• Moves the element
• Skews the element
3. @keyframes is used in CSS to:
• Define transitions
• Define animations
• Define loops
• Define variables

Backend Quiz ( Java/Kotlin ) :

1. What is the default access modifier in Java?
• public
• private
• package-private
• protected
2. Which of these is a Kotlin feature?
• Smart casting
• Manual memory management
• Multiple inheritance
• Pointer arithmetic
3. Java is compiled into:
• Binary code
• Bytecode
• Machine code
• Assembly

Database :

1. Which clause filters rows after grouping?
• WHERE
• GROUP BY
• HAVING
• ORDER BY

Mixed Quiz :

1. Which language is used for both frontend and backend?
• Python
• Java
• JavaScript
• SQL

Weekly Cross-Domain Activities ( June 13 to June 19, 2025 )

API of the Day:

OpenWeatherMap API :

Use the REST Countries API

Task : Build a React app that lets users search a country and shows its flag, capital, and region.

Linux/DevOps Tip :

Top 5 Linux commands for server monitoring:

• top
• htop
• vmstat
• iotop
• netstat -tulpn

Real-World Project of the Week ( June 13 to June 19, 2025 )

Project of the Week:

Build a Task Manager App (Frontend + Backend + DB)

• Use React for UI
• Node.js + Express for API
• PostgreSQL for data persistence

Collaborative Project:

Contribute to the open-source Habit Tracker project on GitHub: github.com/codecrafters-io/habit-tracker.

Case Study:

How Notion Manages Real-Time Collaboration:

• WebSockets, Operational Transform (OT), and React for UI syncing.

Try replicating a collaborative notes editor using Firebase Realtime DB