~/leffloard Türkiye · UTC+3

Systems · Embedded · Web

Mert Kaan Koparan

High-school senior, writing software for 8 years and shipping it to real users. I like the layers most people skip: virtualization, firmware, circuits — and the web apps that sit on top of them. Everything below is designed, built and operated by me.

github.com/leffloard Selected projects
bl_radar.ino — live sweep

// at a glance

Spec sheet

Role
Freelance developer & student
Experience
8 years of code · paid client work since high school
Focus
Embedded systems · low-level C++ · game technology
Core language
C++ (daily driver)
Human languages
Turkish (native) · English (C1) · Japanese (JLPT N5)
Education
High school, Class of 2027 — applying to CS/CE programs in Europe

// selected work

Projects

Each card has expandable technical notes. Private source code — including the hypervisor — can be shared with reviewers on request.

hv — bare-metal hypervisor

active research C++Intel VT-xAMD-VEPT/NPT

A thin hypervisor that virtualizes an already-running operating system on both Intel and AMD hardware, written from scratch in C++. My deepest project: it is where assembly, paging structures and vendor manuals stop being theory.

technical notes
  • Single codebase targeting both vendors: Intel VMX (VT-x) and AMD SVM, behind a common abstraction.
  • Loads under a live Windows instance and demotes it to guest state — no reboot, no custom bootloader required to start virtualizing.
  • Second-level address translation with EPT (Intel) / NPT (AMD), including page-level hooking through those tables.
  • External guest-memory read/write across the virtualization boundary, stable and crash-free under load.
  • In progress: boot-chain integration so the hypervisor can come up before the OS.
private repo · code available on request

Airsoft BLE radar

in development ESP32BLEESP-NOWmobile UI

Field hardware for airsoft matches: an ESP32 scans nearby BLE devices and streams contacts to a phone that renders a game-style rotating radar — designed and built from scratch for real outdoor games with friends.

technical notes
  • Hardware budget: exactly 3× ESP32 (WROOM-32 class) — the design is shaped around what I had on hand.
  • Scanner node sweeps BLE advertisements and forwards contact bearing/strength to the phone client.
  • Planned mesh: extra field-sensor nodes linked over ESP-NOW to extend coverage beyond a single scanner.
  • IFF design: teammates carry a beacon (a dedicated node or their phone) so they render as friendlies, not hostiles.
  • Real-world constraints drive the engineering: battery life, latency and RF behaviour outdoors.
3-node prototype · my own concept, end to end

Subscription & licensing platform

in production Discord botweb panelVPS ops

A commercial reseller system: a Discord bot plus a multi-panel web application. I designed the business rules, built the stack, and operate the production deployment — with paying users.

technical notes
  • Multi-tenancy: one user can own several panels, each with its own state and quotas.
  • Business rules I specified myself: monthly free-key limits counted per panel; granting a still-running panel stacks the new days onto the remaining time.
  • Release workflow: feature branch → merge → deploy to the production server I administer.
  • Running a live product taught me the unglamorous parts: uptime, support, abuse prevention and migrations with real data.
solo-built · live in 2026

BarreFree

planned · open source web appaudio analysisTR/EN

Converts nearly any song into barre-free acoustic guitar arrangements. Built because I play guitar and barre chords are the wall most beginners quit at.

technical notes
  • Inputs: audio upload, pasted chord sheets, or a YouTube/Spotify link.
  • Pipeline: analysis on my own VPS → chord detection → substitution into barre-free voicings.
  • Output: chords and tabs at a user-selected difficulty level; Turkish and English UI.
  • Open source — built first for my own practice, shared for anyone learning acoustic guitar.
music × signal processing

DIY neuro-electronics study

research analog designESP-class MCUUDP

Circuit-level design for a phone-controlled galvanic vestibular stimulation (GVS) device — an exercise in reading papers and turning them into a costed bill of materials.

technical notes
  • Precision current source built around a Howland current pump; op-amp selection for compliance voltage and accuracy.
  • Bidirectional current control via MOSFET switching.
  • ESP-class microcontroller as the bridge; phone control over UDP on the local network.
  • Deliverable so far: complete circuit design plus a costed parts list against components already on hand.
  • Safety first: this is a paper-and-breadboard study — nothing gets attached to a human.
where EE meets neuroscience

Real-time UI engineering

client work C++Dear ImGuirendering

Paid client work modernizing ImGui-based real-time interfaces: visual redesigns plus the rendering and architecture fixes underneath them.

technical notes
  • Modern visual systems: dark themes with accent colors, glass effects and an animation layer.
  • Diagnosed and fixed flicker through frame pacing and animation optimization.
  • Repaired breakages caused by ImGui version incompatibilities.
  • Restructured monolithic code into modular header/source units; separated an authentication subsystem into its own module and integrated it with DLL-based loading, debugging linker-level issues along the way.
performance + aesthetics in immediate-mode UI

// side quests

Smaller builds & infrastructure

Independent uptime watchdogAn ESP32 that monitors my services from outside the server itself — the watcher can't go down with the watched.
Remote PC power controlOptocoupler on the motherboard's power-switch header: safely "press" the button over the network.
Wi-Fi CSI sensingExploring presence/motion detection from Wi-Fi channel state information on ESP32 — no camera needed.
leffloard.wtfPersonal domain on Cloudflare: DNS, subdomain redirect scheme, and this very site.
Server operationsI administer the Windows VPS that runs my production services, deployments and build artifacts.
SenseA Discord community I help run — moderation tooling and day-to-day operations.

// trajectory

Milestones

// toolbox

Skills

Systems & low-level

  • C++ (primary language)
  • x86 virtualization: VT-x, AMD-V
  • EPT/NPT memory management
  • Windows internals
  • Debugging: linkers, crashes, races

Embedded & hardware

  • ESP32 / Arduino firmware
  • BLE, ESP-NOW, UDP networking
  • Analog basics: op-amps, MOSFETs
  • Reading datasheets & papers
  • Breadboard → working prototype

Product & ops

  • Discord bots & web panels
  • VPS deployment & operations
  • Cloudflare DNS & domain ops
  • Git / GitHub workflow
  • Running a product with real users

// off the keyboard

Beyond code

Drawing

Anime-style illustration, colored traditionally with markers.

Music

Acoustic guitar and melodica now; drums as a kid. BarreFree exists because of this.

Reading

Light novels and manga — also my motivation for learning Japanese.

// reach me

Contact

hello@leffloard.wtf github.com/leffloard

Private repositories (incl. the hypervisor) can be shared with reviewers on request.