LoseThos is a "supplemental" operating system because you'll want to dual boot with another operating system, since you can't access the Internet and because it's not really suited for usage other than screwing around writing programs. It's really good for that, though -- lots of
fun. It's very modern except for graphics, being 64-bit and multi-cored. It does not depend on other code for anything. You can put it as the sole operating system on a computer and disconnect the network. For those of you with fierce operating system cult loyalty, relax, it's
not a zero sum game. I promise it will never have networking or run in any mode besides 640x480 16 color. It competes for mind-share, that's about it. It's a less-is-more situation, to some extent.

LoseThos is simple. It runs on a standard 64-bit PC, nothing exotic, and compiles and runs native x86_64 code -- no byte code or interpreter, anywhere. Nervous about no memory protections? You'd be shocked if you knew how many embedded devices operate just fine with no protections. Don't write programs that malfunction. At the worst, you reboot. Takes 2 seconds plus BIOS start-up time.

Features:

64-bit x86, preemptive multitasking, kernel with multicore support. For
Core_i7, Core_2_Duo, Pentium_D... nothing worse than a
Pentium_4_Extreme_Edition.

64-bit compiler/assembler. Nothing is "interpreted."

Free, public domain, and 100% open source.

Source files and the command line window can have graphics, links, icons,
trees, colors, super/sub scripts, margins. Everything is seamless through-out
the tool chain. No need for separate resource files.

Just-in-time compilation. No need for object or exe files.

Graphics in source code. No need for resource files.

64-bit pointers. All memory, even more than 4 Gig, can be directly accessed
by all tasks on all cores at all times.

Highest CPU privileged mode at all times. No off-limits instructions. No
time lost changing modes or address maps. Switches tasks in half a microsecond.

CD/DVD reading and writing, ISO9660 file system.

640x480 16 color VGA graphics.

Boot loaders for CD-ROM and hard disk.

Keyboard & mouse support.

Hard drives, support for FAT32 and LoseThos native file systems with file
compression.

2D/3D Graphics library

Real-time fancy differential-equation solver (physics engine) for use in
games. Adaptive step-size Runge-Kutta, interpolated for real-time.

Tools/utilities including profiler, merge and diff.

HD Audio and many songs.

Demos and documentation.

All source code included. Only compiles with the included LoseThos compiler
and assembler.

Limitations: This is not the latest version. The author now requires a personal email to download it. Good luck with that.