## Problem Build the core logic and frontend for a card-matching memory game. An NxM grid of face-down cards hides N*M/2 pairs. Players flip two cards per turn; a match keeps them face-up, a mismatch flips them back after a short delay. ```ts type Card = { id: number; pairId: number; flipped: boolean; matched: boolean }; class MemoryGame { constructor(public readonly cards: Card[]) {} flip(cardId: number): 'wait' | 'match' | 'no_match' | 'already_flipped' { ... } get moveCount(): number { ... } get isComplete(): boolean { ... } reset(): void { ... } } function createDeck(pairs: number): Card[] { ... } // shuffles cards ``` **Requirements:** Only 2 cards can be in the "pending" state at once. Enforce a delay before non-matching cards are flipped back. ## Follow-ups 1. How do you prevent the user from clicking a third card while the mismatch delay is running? 2. How would you implement the shuffle to guarantee no card is adjacent to its pair? 3. How would you add a high-score board stored in localStorage? 4. How would you animate the flip without using external libraries (CSS 3D transform)?

InterviewDB Experience · San Francisco

Memory Game: Implement the Card-Matching Memory Game with Flip Animation Logic

phone

Interview Experience

Problem Build the core logic and frontend for a card-matching memory game. An NxM grid of face-down cards hides N*M/2 pairs. Players flip two cards per turn; a match keeps them face-up, a mismatch flips them back after a short delay. Requirements: Only 2 cards can be in the "pending" state at once. Enforce a delay before non-matching cards are flipped back. Follow-ups How do you prevent the user from clicking a third card while the mismatch delay is running? How would you implement the shuffle t…

Full Details

🔒

Unlock all Nextdoor questions

Full insider details, leaked discussions, and candidate experiences.

Get full access — from $50/mo

About This Question

This is a candidate experience report from a nextdoor interview during the phone round.

It covers the following topics: Frontend, Phone, Coding, Onsite, Matrix .

Topics

Frontend Phone Coding Onsite Matrix

About Nextdoor Interview Reports

This question was reported by a candidate who interviewed at Nextdoor. LeakCode aggregates interview reports from 10+ sources, including 1Point3Acres, Glassdoor, LeetCode Discuss, Blind, Reddit, Indeed, and Nowcoder. Each report is translated where necessary, deduplicated against existing entries, and tagged by company, role, round type, and reporting date.

Use this question as one calibration data point, not a memorization target. Companies typically rotate their question pools every 2-4 months; the exact wording of a 2024 question may differ from what you encounter today. The underlying pattern, difficulty level, and follow-up depth at Nextdoor are the higher-signal extractions to take from this report.

For broader preparation context, the Nextdoor interview process typically includes a recruiter screen, one or two technical phone screens, and a 4-5 round on-site loop covering coding, system design (at L4+ levels), and behavioral. Reports tagged on LeakCode show the round-by-round distribution and typical difficulty calibration. To browse questions filtered by round type and seniority, use the company hub linked above.

How To Practice This Type of Question

Solve similar problems on LeetCode under timed conditions (25-35 minutes per medium difficulty). The goal is pattern recognition: recognize the underlying technique (sliding window, two-pointer, BFS, memoized recursion, etc.) within 60-90 seconds of reading. Strong candidates verbalize their hypothesis out loud before coding, then iterate based on feedback. Weak candidates dive into implementation immediately, lose time on the wrong approach, and run out of time for follow-ups.

Companies update their question pools every 2-4 months. The exact wording of any given question may have been retired by the time you interview. Focus your prep on the pattern, not the specific problem. The patterns that appear in Nextdoor reports consistently are the ones worth investing in; one-off niche problems are not.

During Your Nextdoor Round

Apply the standard interview round template: clarify requirements (2-3 minutes), state your approach out loud and confirm direction with the interviewer (3-5 minutes), code with narration (15-25 minutes), test with concrete examples including edge cases (5 minutes), discuss optimization or trade-offs if time permits (5 minutes). This template is universally accepted across FAANG and adjacent companies; deviating from it produces weaker interviewer feedback signal.

The single most predictive failure mode in Nextdoor reports tagged "no hire": not asking clarifying questions. Interviewers are explicitly trained to weight this. Strong candidates ask 3-5 clarifying questions even on problems that look obvious; weak candidates dive into code immediately. The clarifying-question check is often the first signal recorded in the interviewer's written notes.