diff --git a/.dockerignore b/.dockerignore
index 4f59329..52f67c3 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -2,3 +2,7 @@
 # excluding a self-contained Go source here drops it from the lint silently.
 # Never exclude Go sources, go.mod/go.sum or .golangci.yml.
 .git
+
+# Generated artifacts only; `make build` puts a multi-megabyte binary here
+# and it would otherwise be shipped into the build context.
+/build/
diff --git a/.gitignore b/.gitignore
index 2b846e1..25aaccd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 *.log
 *.out
 *.test
+/build/
 /rogue
diff --git a/Makefile b/Makefile
index 3bd0b22..fbdcc93 100644
--- a/Makefile
+++ b/Makefile
@@ -6,15 +6,42 @@
 # around the Go toolchain and prettier so `make fmt` / `make check` behave
 # the same as in sneak's other repos.
 
-GO_PKGS  := ./...
-MD_FILES := $(shell git ls-files '*.md')
-PRETTIER := prettier --tab-width 4 --prose-wrap always
+GO_PKGS   := ./...
+MD_FILES  := $(shell git ls-files '*.md')
+PRETTIER  := prettier --tab-width 4 --prose-wrap always
 
-.PHONY: check fmt fmt-check lint test
+# Every generated artifact goes here, and the whole directory is
+# git-ignored. Targets that write outside it can commit their output.
+BUILD_DIR := build
+BIN       := $(BUILD_DIR)/rogue
+COVERPROF := $(BUILD_DIR)/coverage.out
+COVERHTML := $(BUILD_DIR)/coverage.html
 
-# Format, lint, and test — the full local pre-commit gate.
+.PHONY: build check cover cover-html fmt fmt-check lint test
+
+# Format, lint, and test — the full local pre-commit gate. Keep this list
+# to targets that write nothing into the working tree.
 check: fmt-check lint test
 
+# Build the executable into $(BUILD_DIR). `go build -o` does not create the
+# parent directory.
+build:
+	@mkdir -p $(BUILD_DIR)
+	go build -o $(BIN) ./cmd/rogue
+
+# Per-function coverage, for finding which functions are untested. The
+# percentage `make test` prints is a per-package total and cannot answer
+# that. Writes files, so it stays out of `check`.
+cover:
+	@mkdir -p $(BUILD_DIR)
+	go test -timeout 30s -coverprofile=$(COVERPROF) $(GO_PKGS)
+	go tool cover -func=$(COVERPROF)
+
+# Render the same profile as annotated source.
+cover-html: cover
+	go tool cover -html=$(COVERPROF) -o $(COVERHTML)
+	@echo "wrote $(COVERHTML)"
+
 # Format Go and Markdown in place.
 fmt:
 	gofmt -w .
diff --git a/README.md b/README.md
index 691dc81..b7b5ece 100644
--- a/README.md
+++ b/README.md
@@ -21,19 +21,19 @@ original program structure and the design of this port.
 Requires Go 1.25 or later and a terminal at least 80x24.
 
 ```bash
-go build ./cmd/rogue
-./rogue
+make build
+./build/rogue
 ```
 
 ```bash
 # Restore a saved game
-./rogue ~/rogue.save
+./build/rogue ~/rogue.save
 
 # View high scores
-./rogue -s
+./build/rogue -s
 
 # Test the death screen (demo mode)
-./rogue -d
+./build/rogue -d
 ```
 
 ## In-game commands
@@ -57,7 +57,7 @@ Press `?` in game for the full list.
 export ROGUEOPTS="name=YourName,terse,jump,fruit=mango"
 
 # Wizard (debug) mode, with a reproducible dungeon
-ROGUE_WIZARD=1 SEED=12345 ./rogue
+ROGUE_WIZARD=1 SEED=12345 ./build/rogue
 ```
 
 The scoreboard is kept in `~/.rogue.scores`. Save files are Go gob snapshots
@@ -80,9 +80,11 @@ For development, the `Makefile` wraps the toolchain: `make fmt` (gofmt +
 prettier), `make lint` (`script/lint`, which runs golangci-lint inside the
 pinned container built from `Dockerfile.lint` — it is never installed on the
 host, so docker is required), `make test` (the suite, under the race detector
-with coverage and a timeout), and `make check` (all three). Use the targets
-rather than invoking `go test` directly — they carry the flags the project
-relies on.
+with coverage and a timeout), `make check` (all three), `make build` (the
+executable), and `make cover` / `make cover-html` (per-function coverage, and
+the same profile as annotated source at `build/coverage.html`). Everything they
+generate lands in the git-ignored `build/`. Use the targets rather than the
+toolchain directly — they carry the flags the project relies on.
 
 ## License
 
diff --git a/TODO.md b/TODO.md
index 7c2e24c..7d2bc01 100644
--- a/TODO.md
+++ b/TODO.md
@@ -35,6 +35,26 @@ is finished.
 
 # Completed Steps
 
+- 2026-08-10 `make cover` added (https://git.eeqj.de/sneak/rgoue/issues/17).
+  `make cover` writes `build/coverage.out` and prints the per-function report;
+  `make cover-html` renders the same profile to `build/coverage.html`. The
+  per-package percentage `make test` prints cannot say _which_ function is
+  untested, which is how the coverage gaps closed so far had to be found — by
+  grepping test files for identifiers.
+
+    Neither target is in `check`, and neither may be added to it: both write
+    files, and `make check` must not modify the working tree.
+
+- 2026-08-10 `make build` added (https://git.eeqj.de/sneak/rgoue/issues/19). The
+  executable is built to `build/rogue`; `README.md` no longer contains a raw
+  `go` invocation anywhere. `build` is in neither `check` nor `test` —
+  `make check` stays `fmt-check lint test` and still writes nothing into the
+  working tree.
+
+    Generated artifacts now all live under `build/`, which `.gitignore` covers
+    as a whole. Anything written outside it is committable, so a target that
+    puts its output elsewhere reintroduces the stray-artifact problem.
+
 - 2026-08-10 Linting moved into a container
   (https://git.eeqj.de/sneak/rgoue/issues/41). `golangci-lint` is no longer
   invoked on the host anywhere in the repo: `Dockerfile.lint` pins