diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..d1a6f2b
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,40 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  test:
+    name: pytest
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      # erbsland-maze depends on pycairo, which has no Linux wheel and builds
+      # against the system cairo headers.
+      - name: Install system libraries
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libcairo2-dev pkg-config
+
+      # erbsland-maze (the 'maze' extra) depends on pycairo, which has no Linux
+      # wheel and builds against the system cairo headers.
+      - name: Install system libraries
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libcairo2-dev pkg-config
+
+      - name: Install package + dev deps
+        run: |
+          python -m pip install --upgrade pip setuptools
+          python -m pip install ".[dev,maze]"
+          python -m pip list
+
+      - name: Run tests
+        run: python -m pytest -q
diff --git a/README.md b/README.md
index ce9a237..bc719f5 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,7 @@ Getting started
 This library is available from PyPi as `rollingmill`.
 
     $ pip install rollingmill
+    $ pip install "rollingmill[maze]"                        # adds maze generator (needs cairo headers on Linux)
     $ rollingmill                                            # launch TUI on real hardware
     $ rollingmill --file sample-nc/example-doc-part.gcode    # stream an NC file
 
diff --git a/pyproject.toml b/pyproject.toml
index 290cfdf..4c73ef3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -33,7 +33,6 @@ classifiers = [
 dependencies = [
     "pyusb>=1.2",
     "pyhershey>=0.1",
-    "erbsland-maze>=1.4.8",
     "setuptools",          # pyhershey imports pkg_resources; drop when upstream moves to importlib.metadata
 ]
 
@@ -44,6 +43,9 @@ dev = [
     "ruff>=0.6",
     "mypy>=1.10",
 ]
+maze = [
+    "erbsland-maze>=1.4.8",   # imports pycairo, which builds against system cairo on Linux
+]
 
 [project.scripts]
 rollingmill = "rollingmill.tui:main"
diff --git a/rollingmill/maze.py b/rollingmill/maze.py
index 646c77c..60618f3 100644
--- a/rollingmill/maze.py
+++ b/rollingmill/maze.py
@@ -20,18 +20,23 @@
 from pathlib import Path
 from typing import Iterable
 
-from erbsland_maze import (
-    Direction,
-    Generator,
-    GeneratorSetup,
-    Room,
-    SvgLayout,
-    SvgSetup,
-    Wall,
-)
-from erbsland_maze.line import Line
-from erbsland_maze.point import Point
-from erbsland_maze.poly_line import PolyLine
+try:
+    from erbsland_maze import (
+        Direction,
+        Generator,
+        GeneratorSetup,
+        Room,
+        SvgLayout,
+        SvgSetup,
+        Wall,
+    )
+    from erbsland_maze.line import Line
+    from erbsland_maze.point import Point
+    from erbsland_maze.poly_line import PolyLine
+except ImportError as exc:  # pragma: no cover - exercised only without the extra
+    raise ImportError(
+        "rollingmill.maze needs the 'maze' extra: pip install 'rollingmill[maze]'"
+    ) from exc
 
 
 ENDPOINT_MODES = ("none", "outline", "filled")
diff --git a/tests/test_cutjob_state.py b/tests/test_cutjob_state.py
index fbbb7ea..69816d3 100644
--- a/tests/test_cutjob_state.py
+++ b/tests/test_cutjob_state.py
@@ -38,7 +38,7 @@ def bulk_write(self, data: bytes) -> int:
         return len(data)
 
 
-def _new_job(payload: bytes = b'G0X0\rG0Y0\rG0Z0\r') -> CutJob:
+def _new_job(payload: bytes = b'G00 X0.0\rG00 Y0.0\rG00 Z0.0\r') -> CutJob:
     m = MDX40A(_AckingMockUSB())
     return CutJob.from_bytes(m, payload, 'test.nc')
 
@@ -156,17 +156,17 @@ def test_parse_nc_blocks_does_not_validate():
 def test_check_nc_accepts_parse_nc_blocks_output_directly():
     """check_nc takes the raw bytes output of parse_nc_blocks; no decoding
     needed at the call site."""
-    blocks = parse_nc_blocks(b"(hello)\nG01 X1.0\n(more)\n")
+    blocks = parse_nc_blocks(b"(hello)\nG00 X1.0\n(more)\n")
     assert list(check_nc(blocks)) == []
 
 
 def test_check_nc_clean_file_returns_no_warnings():
-    blocks = [b"(hello)\n", b"G01 X1.0\n", b"(more)\n"]
+    blocks = [b"(hello)\n", b"G00 X1.0\n", b"(more)\n"]
     assert list(check_nc(blocks)) == []
 
 
 def test_check_nc_flags_embedded_close_paren():
-    blocks = [b"G01 X1.0\n", b"(this (is) bad)\n", b"G01 Y2.0\n"]
+    blocks = [b"G00 X1.0\n", b"(this (is) bad)\n", b"G00 Y2.0\n"]
     warnings = check_nc(blocks)
     assert len(warnings) == 1
     w = warnings[0]
@@ -182,19 +182,19 @@ def test_check_nc_flags_embedded_open_paren():
 
 
 def test_check_nc_flags_unclosed_comment():
-    blocks = [b"G01 X1.0\n", b"G01 Y2.0\n", b"(forgot to close\n",
-              b"G01 Z3.0\n"]
+    blocks = [b"G00 X1.0\n", b"G00 Y2.0\n", b"(forgot to close\n",
+              b"G00 Z3.0\n"]
     warnings = check_nc(blocks)
     assert len(warnings) == 1
     assert warnings[0].rule == RULE_PAREN_UNCLOSED
     assert warnings[0].line == 3
 
 
-def test_check_nc_ignores_parens_in_non_comment_lines():
-    # A code line that happens to contain '(' or ')' mid-stream is NOT
-    # subject to the rule -- only lines that *start* with '(' are
-    # treated as comments by the firmware.
-    assert list(check_nc([b"G01 X1.0 ( inline ) F100\n"])) == []
+def test_check_nc_paren_rules_ignore_non_comment_lines():
+    # A code line that happens to contain '(' or ')' mid-stream is not a
+    # comment line, so rules 1 and 2 do not apply (rule 5 flags it instead).
+    warnings = check_nc([b"G00 X1.0 ( inline ) F100\n"])
+    assert [w.rule for w in warnings] == [5]
 
 
 def test_check_nc_locates_column_of_first_embedded_paren():
@@ -211,7 +211,7 @@ def test_check_nc_accepts_empty_comment():
 
 def test_check_nc_reports_all_warnings_not_just_first():
     """The lint should surface every issue so the user can fix in one pass."""
-    blocks = [b"(bad (one))\n", b"G01 X1.0\n", b"(unclosed\n"]
+    blocks = [b"(bad (one))\n", b"G00 X1.0\n", b"(unclosed\n"]
     warnings = check_nc(blocks)
     assert len(warnings) == 2
     rules = sorted(w.rule for w in warnings)
@@ -231,7 +231,7 @@ def test_from_bytes_rejects_files_with_warnings():
 
 def test_main_clean_file_returns_zero(tmp_path, capsys):
     p = tmp_path / "clean.nc"
-    p.write_bytes(b"(ok)\nG01 X1.0\n")
+    p.write_bytes(b"(ok)\nG00 X1.0\n")
     rc = check_main([str(p)])
     out = capsys.readouterr().out
     assert rc == 0
@@ -243,7 +243,7 @@ def test_main_reports_warnings_in_three_line_format(tmp_path, capsys):
     three lines per warning (header, source, caret). capsys captures
     non-TTY stdout, so ANSI codes are absent."""
     p = tmp_path / "bad.nc"
-    p.write_bytes(b"G01 X1.0\n(bad (paren))\n")
+    p.write_bytes(b"G00 X1.0\n(bad (paren))\n")
     rc = check_main([str(p)])
     captured = capsys.readouterr()
     assert rc == 1
@@ -276,7 +276,7 @@ def test_tui_main_bails_on_bad_file_before_usb(tmp_path, monkeypatch, capsys):
     warnings and exit *before* MdxUSB.discover() is invoked — there's no
     point handshaking the mill only to abort after reading the file."""
     p = tmp_path / "bad.nc"
-    p.write_bytes(b"G01 X1.0\n(bad (paren))\n")
+    p.write_bytes(b"G00 X1.0\n(bad (paren))\n")
 
     # Sentinel that fails the test if USB discovery is reached.
     from rollingmill import usb as usb_mod
diff --git a/tests/test_sleep_inhibit.py b/tests/test_sleep_inhibit.py
index e57e13b..23d7a2c 100644
--- a/tests/test_sleep_inhibit.py
+++ b/tests/test_sleep_inhibit.py
@@ -159,7 +159,7 @@ def rel():
     return counts
 
 
-def _new_job(payload: bytes = b'G0X0\rG0Y0\rG0Z0\r') -> CutJob:
+def _new_job(payload: bytes = b'G00 X0.0\rG00 Y0.0\rG00 Z0.0\r') -> CutJob:
     return CutJob.from_bytes(MDX40A(_AckingMockUSB()), payload, 'test.nc')