Introduction

What is acodeaday?

acodeaday is a daily coding practice app that uses spaced repetition to help you master coding interview problems. Instead of cramming, you solve one new problem per day plus review problems at optimal intervals for long-term retention.

Core Philosophy

"An apple a day keeps the doctor away" "A code a day keeps rejection away"

The app is designed around the principle of understanding through consistent practice, not cramming. By spacing out your practice and reviewing problems at scientifically-proven intervals, you build lasting knowledge of coding patterns and problem-solving techniques.

How It Works

Daily Session

Each day, you'll see up to 3 problems:

1. Review #1: Your oldest overdue problem (if any)
2. Review #2: Your second oldest overdue problem (if any)
3. New Problem: The next unsolved problem in sequence

Spaced Repetition (Anki SM-2)

The app uses the Anki SM-2 algorithm with adaptive intervals based on difficulty ratings:

After solving a problem, you rate how difficult it was:

• Again: Reset to 1 day (struggled/needed hints)
• Hard: Slower growth (×1.2), decrease ease factor
• Good: Normal growth (×ease factor)
• Mastered: Exit rotation immediately

                    ┌─────────────┐
                    │   Unsolved  │
                    └──────┬──────┘
                           │
                      Solve & rate
                           │
                           ▼
                    ┌─────────────┐
                    │  In Review  │◄─────────────┐
                    │ (scheduled) │              │
                    └──────┬──────┘              │
                           │                     │
                    Interval ≥30d          "Show Again"
                    or "Mastered"                │
                           │                     │
                           ▼                     │
                    ┌─────────────┐              │
                    │  Mastered   │──────────────┘
                    └─────────────┘

Tech Stack

Component	Technology
Backend	FastAPI (Python 3.13+) with async SQLAlchemy 2.0
Frontend	TanStack (React 19) with TanStack Router/Query
Code Editor	Monaco Editor
Code Execution	Judge0 CE (self-hosted)
Database	Supabase PostgreSQL
Auth	Supabase Auth (JWT Bearer tokens)
AI Chat	litellm (Gemini, OpenAI, Anthropic)
Package Manager	uv (Python), npm (JavaScript)

Key Features

• LeetCode-style interface: Familiar split-pane layout with problem description and code editor
• Secure code execution: All code runs in Judge0 sandboxed environment
• Progress tracking: See your mastery progress across all problems
• Submission history: Review your past attempts and solutions
• AI-powered assistance: Get hints and explanations from AI tutors when you're stuck
• Multiple test modes: Run code against example tests, or submit against all tests

Architecture

┌──────────┐       ┌─────────────────┐       ┌─────────────────┐
│  Client  │──────▶│  FastAPI        │──────▶│ Judge0 (Docker) │
│ (React)  │       │  Backend        │       │                 │
└──────────┘       └─────────────────┘       └─────────────────┘
                           │
                           ▼
                   ┌─────────────────┐
                   │ Supabase        │
                   │ PostgreSQL      │
                   └─────────────────┘

Current Features

The implementation includes:

• 16 Blind 75 problems seeded and ready to practice
• Python support with JavaScript coming soon
• Anki SM-2 spaced repetition with difficulty ratings
• Monaco editor with auto-save
• Self-hosted Judge0 for secure code execution
• AI Chat assistant for hints and explanations (Socratic or direct mode)
• Submission history to review past attempts

Next Steps

Ready to get started? Head over to the Quick Start guide to set up acodeaday locally.