JS Arena: Java practice with an AI teacher that teaches, not solves
Coding practice sites tell beginners they are wrong but not why, and chatbots give away the full answer, so students copy and learn nothing. JS Arena fixes both.

Students write real Java in an in-browser editor and get exact verdicts: Accepted, Wrong Answer, Compilation Error, Runtime Error or Time Limit Exceeded. An AI tutor sees their current code and last result, finds the mistake, and dry runs the code step by step, but refuses to hand over the full solution. After a solution is accepted, the platform estimates its time and space complexity and suggests how to improve it.

Scoring is honest: 80 marks per problem, minus 20 for a hint or 60 for unlocking the solution. A dashboard shows progress, streaks and a yearly activity heatmap. Admins can generate new problems with AI, and every test’s expected output is checked by actually running a reference solution.

Tech: React, Vite, GSAP, Express, MongoDB, Gemini, Docker, Render. Each user brings their own encrypted API key.

Live: https://hactober-fest.onrender.com