Update README.md

README.md

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-# popcorn: A toy microkernel x64 UEFI OS 
+# popcorn: A toy OS kernel
 
-**popcorn** is a hobby OS for x64 UEFI environments to play with building a
-microkenerl architecture. It's far from finished, or even being usable - for
-now, it's a sandbox for me to explore the UEFI architecture, microkernels, and
-OS-related concepts that I want to play with.
+**popcorn** is the kernel for the hobby OS that I am currently building. It's
+far from finished, or even being usable. Instead, it's a sandbox for me to play
+with kernel-level code and explore architectures.
 
+The design goals of the project are:
+
+* Modernity - I'm not interested in designing for legacy systems, or running on
+  all hardware out there. My target is only 64 bit architecutres, and modern
+  commodity hardware. Currently that means x64 systems with Nehalem or newer
+  CPUs and UEFI firmware. Eventually I'd like to work on an AArch64 port,
+  partly to force myself to factor out the architecture-dependent pieces of the
+  code base.
+
+* Modularity - I'd like to pull as much of the system out into separate
+  processes as possible, in the microkernel fashion. A sub-goal of this is to
+  explore where the bottlenecks of such a microkernel are now, and whether
+  eschewing legacy hardware will let me design a system that's less bogged down
+  by the traditional microkernel problems. Given that there are no processes
+  yet, the kernel is monolithic by default.
+
+* Exploration - I'm really mostly doing this to have fun learning and exploring
+  modern OS development. Modular design may be tossed out (hopefully
+  temporarily) in some places to allow me to play around with the related
+  hardware.
+
+## Building
+
+Popcorn uses the `waf` build tool, which is included in the repo. The other
+requirements are:
+
+* python (to run waf)
+* gcc
+* nasm
+
+After cloning, run `waf configure`. Then you can run `waf build` to build the
+project, and `waf test` to run the tests. A floppy disk image will be built in
+`build/popcorn.img`. If you have `qemu-system-x86_64` installed, then you can
+run `waf qemu` to run it in `-nographic` mode.