diff --git a/.idea/dictionaries/ericf.xml b/.idea/dictionaries/ericf.xml
index 5e46b2e7..fcb5af3b 100644
--- a/.idea/dictionaries/ericf.xml
+++ b/.idea/dictionaries/ericf.xml
@@ -54,6 +54,7 @@
       <w>anroid</w>
       <w>antigravity</w>
       <w>apichanges</w>
+      <w>apis</w>
       <w>apks</w>
       <w>appcfg</w>
       <w>appconfig</w>
@@ -934,6 +935,7 @@
       <w>minigames</w>
       <w>minusbutton</w>
       <w>minval</w>
+      <w>minver</w>
       <w>mios</w>
       <w>mipmap</w>
       <w>mipmaps</w>
@@ -1689,6 +1691,7 @@
       <w>vmshell</w>
       <w>vmware</w>
       <w>vmwarevm</w>
+      <w>vnums</w>
       <w>vobj</w>
       <w>voffs</w>
       <w>vorbis</w>
@@ -1696,6 +1699,7 @@
       <w>vrmode</w>
       <w>vrtesting</w>
       <w>vscode</w>
+      <w>vstr</w>
       <w>vsync</w>
       <w>vsyncs</w>
       <w>vval</w>
diff --git a/Makefile b/Makefile
index 039aeb9f..80509e66 100644
--- a/Makefile
+++ b/Makefile
@@ -36,7 +36,7 @@ DOCPREFIX = "ballisticacore_"
 ################################################################################
 
 # List targets in this Makefile and basic descriptions for them.
-help: list
+help:
 	@tools/snippets makefile_target_list Makefile
 
 # Prerequisites that should be in place before running most any other build;
@@ -448,7 +448,7 @@ TOOL_CFG_SRC = tools/efrotools/snippets.py config/config.json
 .pycheckers: config/toolconfigsrc/pycheckers ${TOOL_CFG_SRC}
 	${TOOL_CFG_INST} $< $@
 
-.cache/checkenv:
+.cache/checkenv: tools/snippets
 	@tools/snippets checkenv
 	@mkdir -p .cache
 	@touch .cache/checkenv
diff --git a/tools/efrotools/efrocache.py b/tools/efrotools/efrocache.py
index c111e68b..acf55684 100644
--- a/tools/efrotools/efrocache.py
+++ b/tools/efrotools/efrocache.py
@@ -210,7 +210,7 @@ def update_cache(makefile_dirs: List[str]) -> None:
 
     # Push what we just wrote to the staging server
     print('Pushing cache to staging...', flush=True)
-    run('rsync --recursive build/efrocache/'
+    run('rsync --progress --recursive build/efrocache/'
         ' ubuntu@ballistica.net:files.ballistica.net/cache/ba1/')
 
     print(f'Cache update successful!')
diff --git a/tools/snippets b/tools/snippets
index 633dde22..1cf147eb 100755
--- a/tools/snippets
+++ b/tools/snippets
@@ -49,7 +49,7 @@ from efrotools.snippets import (  # pylint: disable=unused-import
     compile_python_files)
 
 if TYPE_CHECKING:
-    from typing import Optional, List
+    from typing import Optional, List, Sequence
 
 # Parts of full-tests suite we only run on particular days.
 # (This runs in listed order so should be randomized by hand to avoid
@@ -640,11 +640,63 @@ def warm_start_asset_build() -> None:
             check=True)
 
 
+def _vstr(nums: Sequence[int]) -> str:
+    return '.'.join(str(i) for i in nums)
+
+
 def checkenv() -> None:
     """Check for tools necessary to build and run the app."""
-    if subprocess.run(['which', 'python3.7'], check=False,
+    print('Checking environment...', flush=True)
+
+    python_bin = 'python3.7'
+    pylint_min_ver = [2, 4, 3]
+    mypy_min_ver = [0, 740]
+
+    # Make sure they've got our target python version.
+    if subprocess.run(['which', python_bin], check=False,
                       capture_output=True).returncode != 0:
-        raise CleanError('python3.7 is required for these builds.')
+        raise CleanError(f'{python_bin} is required.')
+
+    # Make sure they've got pip for that python version.
+    if subprocess.run(f"{python_bin} -m pip --version",
+                      shell=True,
+                      check=False,
+                      capture_output=True).returncode != 0:
+        raise CleanError('pip (for {python_bin}) is required.')
+
+    # Check for some required python modules.
+    for modname, minver in [
+        ('pylint', pylint_min_ver),
+        ('mypy', mypy_min_ver),
+        ('typing_extensions', None),
+        ('pytz', None),
+    ]:
+
+        if minver is not None:
+            results = subprocess.run(f'{python_bin} -m {modname} --version',
+                                     shell=True,
+                                     check=False,
+                                     capture_output=True)
+        else:
+            results = subprocess.run(f'{python_bin} -c "import {modname}"',
+                                     shell=True,
+                                     check=False,
+                                     capture_output=True)
+        if results.returncode != 0:
+            raise CleanError(
+                f'{modname} (for {python_bin}) is required.\n'
+                f'To install it, try: "{python_bin} -m pip install {modname}"')
+        if minver is not None:
+            ver_line = results.stdout.decode().splitlines()[0]
+            assert modname in ver_line
+            vnums = [int(x) for x in ver_line.split()[-1].split('.')]
+            assert len(vnums) == len(minver)
+            if vnums < minver:
+                raise CleanError(
+                    f'{modname} ver. {_vstr(minver)} or newer required;'
+                    f' found {_vstr(vnums)}')
+
+    print('Environment ok.', flush=True)
 
 
 def make_prefab() -> None: