cannon: update readme, no need for makefile anymore

cannon/Makefile

-SHELL := /bin/bash
-
-build: contracts
-.PHONY: build
-
-contracts:
-	cd contracts && forge build
-.PHONY: contracts
-
-test:
-	cd mipsevm && go test -v ./...
-.PHONY: test

cannon/README.md

 <!--![cannon](https://upload.wikimedia.org/wikipedia/commons/8/80/Cannon%2C_Château_du_Haut-Koenigsbourg%2C_France.jpg)-->
 <!--![cannon](https://cdn1.epicgames.com/ue/product/Featured/SCIFIWEAPONBUNDLE_featured-894x488-83fbc936b6d86edcbbe892b1a6780224.png)-->
 <!--![cannon](https://static.wikia.nocookie.net/ageofempires/images/8/80/Bombard_cannon_aoe2DE.png/revision/latest/top-crop/width/360/height/360?cb=20200331021834)-->
-![cannon](https://paradacreativa.es/wp-content/uploads/2021/05/Canon-orbital-GTA-01.jpg)
+<!--![cannon](https://paradacreativa.es/wp-content/uploads/2021/05/Canon-orbital-GTA-01.jpg)-->
 
 ---
 
@@ -17,25 +17,73 @@ one instruction at a time, as part of an interactive dispute game.
 
 For more information, see [Docs](./docs/README.md).
 
-## Directory Layout
+## Usage
 
-```
-contracts -- A MIPS emulator implementation, using merkleized state and a pre-image oracle.
-example   -- Example programs that can be run and proven with Cannon.
-extra     -- Extra scripts and legacy contracts, deprecated.
-mipsevm   -- Go tooling to test the onchain MIPS implementation, and generate proof data.
-diffmips  -- MIPS diff testing, to ensure correctness of the main Cannon implementation, with isolated dependencies. 
-```
+```shell
+# Build op-program server-mode and MIPS-client binaries.
+cd ../op-program
+make op-program # build
 
-## Building
+# Switch back to cannon, and build the CLI
+cd ../cannon
+go build -o cannon .
 
-### `contracts`
+# Transform MIPS op-program client binary into first VM state.
+# This outputs state.json (VM state) and meta.json (for debug symbols).
+./cannon load-elf --path=../optimism/op-program/bin/op-program-client.elf
 
-The contracts are compiled with [`forge`](https://github.com/foundry-rs/foundry).
-```
-make contracts
+# Run cannon emulator (with example inputs)
+# Note that the server-mode op-program command is passed into cannon (after the --),
+# it runs as sub-process to provide the pre-image data.
+#
+# Note:
+#  - The L2 RPC is an archive L2 node on OP goerli.
+#  - The L1 RPC is a non-archive RPC, also change `--l1.rpckind` to reflect the correct L1 RPC type.
+./cannon run
+--pprof.cpu
+--info-at '%10000000'
+--proof-at never
+--input ./state.json
+--
+../optimism/op-program/bin/op-program
+--l2 ws://127.0.0.1:8746
+--l1 ws://127.0.0.1:8646
+--l1.trustrpc
+--l1.rpckind debug_geth
+--log.format terminal
+--l2.head 0xedc79de4d616a9100fdd42192224580daee81ea3d6303de8089d48a6c1bf4816
+--network goerli
+--l1.head 0x204f815790ca3bb43526ad60ebcc64784ec809bdc3550e82b54a0172f981efab
+--l2.claim 0x530658ab1b1b3ff4829731fc8d5955f0e6b8410db2cd65b572067ba58df1f2b9
+--l2.blocknumber 8813570
+--datadir /tmp/fpp-database
+--server
+
+# Add --proof-at '=12345' (or pick other pattern, see --help)
+# to pick a step to build a proof for (e.g. exact step, every N steps, etc.)
+
+# Also see `./cannon run --help` for more options
 ```
 
+## Contracts
+
+The Cannon contracts:
+- `MIPS.sol`: A MIPS emulator implementation, to run a single instruction onchain, with merkleized VM memory.
+- `Oracle.sol`: implements the pre-image oracle ABI, to support the instruction execution pre-image requests.
+
+The smart-contracts are integrated into the Optimism monorepo contracts:
+[`../packages/contracts-bedrock/contracts/cannon`](../packages/contracts-bedrock/contracts/cannon)
+
+## `mipsevm`
+
+`mipsevm` is Go tooling to test the onchain MIPS implementation, and generate proof data.
+
+## `example`
+
+Example programs that can be run and proven with Cannon.
+Optional dependency, but required for `mipsevm` Go tests.
+See [`example/Makefile`](./example/Makefile) for building the example MIPS binaries.
+
 ## License
 
 MIT, see [`LICENSE`](./LICENSE) file.