Spent the almost 7 hours building a bare-metal, 32-bit RISC-V CPU emulator entirely in Rust from scratch! I finished the core RV32I instruction decoding and set up a simulated 1MB memory array, but getting actual C code to run on it was a massive challenge. I ran into two brutal bugs: The GCC cross-compiler was secretly compressing my instructions into 16-bit chunks, causing my 32-bit fetch() cycle to mash instructions together into unknown opcodes. I had to configure -march=rv32i to force strict 32-bit mode. My CPU tried to jump to an address 4.2 billion bytes out of bounds because of a 64-bit sign-extension trap in Rust! After fixing those, I wrote a tiny bootloader routine to set the Stack Pointer (x2), built a proxy-kernel to handle ecall system traps, and set up Memory-Mapped I/O (MMIO). The emulator can now successfully run a freestanding C program, print to a fake terminal screen, and exit cleanly!