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cs4140 Notes: 12-03 Semester Review

·440 words·3 mins·

CS4140 Fall 2025: Semester Review
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Class Goals and Structure
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Software Engineering focuses on building large projects in teams:

  • Agile practices (Kanban via Taiga.io).
  • GitHub workflow: Forks, feature branches, PR reviews.
  • Continuous Integration/Deployment (GitHub Actions).
  • Tools: Inkfish (attendance/assignments), Aider + OpenRouter (LLM coding assist).
  • One big team project: Shard, a web-based MUD (Multi-User Dungeon) with federation goals.
  • Weekly lectures + in-class demos + Taiga stories.

New this semester:

  • Heavy LLM use for code generation/tests (Aider).
  • Vague agile: Collaborative planning, customer talks (in-class), CI/CD.

Tech Stack
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  • Backend: Elixir/Phoenix (OTP for concurrency/reliability).
    • Ecto/Postgres for DB.
    • Channels/LiveView for real-time.
    • GenServers/Supervisors/Registry for game state.
  • Frontend: HEEx templates + React (via esbuild/pnpm).
  • Deployment: Ubuntu VPS (RackNerd/etc.), Nginx, Systemd, prod releases.
  • Other: Tailwind/Flowbite, Swoosh (email), SQLite for demos.

Project Timeline: Shard
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Weeks 1-3: Setup & Basics
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  • GitHub org (psu-cs4140/shard), Taiga board.
  • mix phx.new shard.
  • Add users/auth (phx.gen.auth), admins.
  • CRUD demo (Goats).
  • Deploy to shard.homework.quest (VPS checklist: ASDF, env vars, systemd).

Weeks 4-6: UI & Real-time
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  • LiveView/Channels for forms/comments.
  • React integration (invites list via AJAX).
  • Game design: Rooms, zones, chars/mobs/items.
  • Async events (GenServer for goblin fights/healing).

Weeks 7-9: Process & Quality
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  • Strict PR rules: Single topic, tests preserved, coverage up.
  • CI: mix format --check, mix test --cover (20%+), Credo (style/max file length).
  • Hangman demo: React -> Channel -> GenServer (multiplayer, named games, DB scores).

Weeks 10-12: Features & Polish
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  • Email: Mailjet API for auth links.
  • Invite codes/links.
  • Licensing audit, dep security (left-pad, supply chain attacks).
  • Performance: TCP slow-start, TTFB, Pagespeed, caching.

Weeks 13+: Advanced Topics
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  • LLMs: Tokens/embeddings, training/inference, quantization (Q4_K), llama.cpp/OpenAI API.
    • Run local (CPU/GPU), browser (bchat demo).
    • Integration: LangChain/Elixir for tools/agents.
  • Scaling/Replication: Indexes, read replicas, sharding, CAP theorem, NoSQL (CouchDB/Riak/Cockroach).
  • Distributed State: Byzantine Generals, single-source truth (server authoritative).
  • Final features: Admin invites, zones/quests, multiplayer playtest.

Key Lessons
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Agile/Process
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  • Kanban > Waterfall for discovery-heavy projects.
  • PR checklists prevent merge hell.
  • Coverage/Credo/format in CI catches issues early.
  • LLM (Aider) accelerates boilerplate/tests, but review outputs.

Elixir/Phoenix Strengths
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  • OTP shines for game servers (fault-tolerant, concurrent).
  • LiveView/Chans simplify real-time vs. React+WebSockets.
  • Deployment straightforward (releases beat Docker for small VPS).

Challenges & Wins
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  • Wins: Deployed game early, multiplayer Hangman, email auth, CI at 90%+ coverage.
  • Challenges: File bloat (refactor!), dep audits, scaling DB reads.
  • LLM Impact: $5-55/student; sped prototyping, but Elixir learning curve persists.
  • Security: Auth, supply chain (npm graph horror), replication/backup.

Final Deliverables
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  • Midterm reports: Progress, LLM spend, Elixir comfort.
  • Advanced features (teams): Zones, federation(?), scaling.
  • Presentations: Dec 12 (demo your feature/zone).

Next Steps
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  • Playtest Friday.
  • Deploy finals, reflect on agile/LLM.
  • Post-class: Shard federation, prod scaling?

Thanks for a great semester—built a real game as a team!

Nat Tuck
Author
Nat Tuck