Embedded Systems Engineer - Custom Firmware for Coin-Op Arcade Machine (Fixed Price $500)

We own and operate a small chain of coin-operated arcade machines (punch/strength testers) and are hiring a developer to upgrade the electronics and add new features to them. Each unit is built around a small microcontroller board (ATmega or STM family), a force/load sensor for measuring punch strength, a numeric display, a coin mechanism, and a small speaker. We're looking for someone to build out the features below for our machines. What we're hoping to build, in order of priority: 1) Custom scoring logic. We want full control over how a punch translates into a score, including the ability to set our own range and spread, since we use scoring to rank players. 2) Scheduled power-off. The unit should be able to shut itself down automatically at a set time each day. 3) Adjustable play settings. A simple way, like a dip switch bank, to change how many coins or how much money buys how many punches, adjustable per location without reflashing anything. 4) Persistent coin count. A running total of coins inserted, saved to onboard memory so it survives a power cycle, so cash collected matches what's logged. 5) Custom audio (nice to have). Our own sound instead of whatever currently plays, understanding this may need extra hardware depending on memory limits. Fine as a stretch goal or separate quote. A couple of logistics notes: you won't need a physical unit in hand to submit a proposal. Photos and video should be enough to scope feasibility, and we can ship a unit, or just the relevant electronics, once we've agreed on an approach. Budget is a fixed $500 covering the scope above. If that's tight for everything listed, we're happy to hear a proposal that covers items 1 and 2 first, with the rest quoted as a follow-on. When you apply, let us know roughly how you'd split your hours across the tasks above, and share any past work building custom firmware, working with sensor-based input, or building original electronics projects. We're actively expanding this business, so there's real potential for repeat work, and possibly a fully custom build with us later on.