diff --git a/BUGS.md b/BUGS.md
index 7a8a4ce..34ee95a 100644
--- a/BUGS.md
+++ b/BUGS.md
@@ -1,31 +1,10 @@
 
 # BUGS
 
-
-Traceback (most recent call last):
-  File "/home/mjsb/.local/lib/python3.7/site-packages/tornado/web.py", line 1697, in _execute
-    result = method(*self.path_args, **self.path_kwargs)
-  File "/home/mjsb/.local/lib/python3.7/site-packages/tornado/web.py", line 3174, in wrapper
-    return method(self, *args, **kwargs)
-  File "/usr/home/mjsb/Work/Projects/aprendizations/aprendizations/serve.py", line 213, in get
-    self.learn.start_course(uid, course)
-  File "/usr/home/mjsb/Work/Projects/aprendizations/aprendizations/learnapp.py", line 275, in start_course
-    student.start_course(course)
-  File "/usr/home/mjsb/Work/Projects/aprendizations/aprendizations/student.py", line 57, in start_course
-    self.topic_sequence = self.recommend_topic_sequence(topics)
-  File "/usr/home/mjsb/Work/Projects/aprendizations/aprendizations/student.py", line 216, in recommend_topic_sequence
-    ts.update(nx.ancestors(G, t))
-  File "/home/mjsb/.local/lib/python3.7/site-packages/networkx/algorithms/dag.py", line 92, in ancestors
-    raise nx.NetworkXError("The node %s is not in the graph." % source)
-networkx.exception.NetworkXError: The node programming/languages/pseudo-tcg/functions-produtorio is not in the graph.
-
-- detectar se em courses.yaml falta declarar ficheiro. Por exemplo se houver goals que não estao em lado nenhum.
+- nao esta a seguir o max_tries definido no ficheiro de dependencias.
 - registar last_seen e remover os antigos de cada vez que houver um login.
 - initdb da integrity error se no mesmo comando existirem alunos repetidos (p.ex em ficheiros csv diferentes ou entre csv e opcao -a)
-- permite definir goal, mas nao verifica se esta no grafo. rebenta no start_topic.
 - double click submits twice.
-- nao esta a seguir o max_tries definido no ficheiro de dependencias.
-- impedir que quando students.db não é encontrado, crie um ficheiro vazio.
 - classificacoes so devia mostrar os que ja fizeram alguma coisa
 - QFactory.generate() devia fazer run da gen_async, ou remover.
 - marking all options right in a radio question breaks!
@@ -70,6 +49,8 @@ sqlite3.ProgrammingError: SQLite objects created in a thread can only be used in
 
 # FIXED
 
+- impedir que quando students.db não é encontrado, crie um ficheiro vazio.
+- permite definir goal, mas nao verifica se esta no grafo. rebenta no start_topic.
 - se num topico, a ultima pergunta tem imagens, o servidor nao fornece as imagengs porque o current_topic passa a None antes de carregar no botao continuar. O caminho é prefix+None e dá erro.
 - caixas com os cursos não se ajustam bem com ecran estreito.
 - obter rankings por curso GET course=course_id
diff --git a/aprendizations/learnapp.py b/aprendizations/learnapp.py
index e8bbc00..7ae92ce 100644
--- a/aprendizations/learnapp.py
+++ b/aprendizations/learnapp.py
@@ -69,28 +69,37 @@ class LearnApp(object):
 
         config: Dict[str, Any] = load_yaml(courses)
 
-        # --- courses dict
-        self.courses = config['courses']
-        logger.info(f'Courses: {", ".join(self.courses.keys())}')
-
         # --- topic dependencies are shared between all courses
         self.deps = nx.DiGraph(prefix=prefix)
-        logger.info('Populating graph:')
+        logger.info('Populating topic graph:')
 
         t = config.get('topics', {})  # topics defined directly in courses file
         self.populate_graph(t)
         logger.info(f'{len(t):>6} topics in {courses}')
         for f in config.get('topics_from', []):
             c = load_yaml(f)    # course configuration
+
+            # FIXME set defaults??
             logger.info(f'{len(c["topics"]):>6} topics imported from {f}')
             self.populate_graph(c)
         logger.info(f'Graph has {len(self.deps)} topics')
 
+        # --- courses dict
+        self.courses = config['courses']
+        logger.info(f'Courses:  {", ".join(self.courses.keys())}')
+        for c, d in self.courses.items():
+            for goal in d['goals']:
+                if goal not in self.deps.nodes():
+                    # logger.error(f'Goal "{goal}" of "{c}"" not in the graph')
+                    raise LearnException(f'Goal "{goal}" from course "{c}" '
+                                         ' does not exist')
+
         # --- factory is a dict with question generators for all topics
         self.factory: Dict[str, QFactory] = self.make_factory()
 
         # if graph has topics that are not in the database, add them
-        self.db_add_missing_topics(self.deps.nodes())
+        self.add_missing_topics(self.deps.nodes())
+
 
         if check:
             self.sanity_check_questions()
@@ -301,7 +310,7 @@ class LearnApp(object):
     # ------------------------------------------------------------------------
     # Fill db table 'Topic' with topics from the graph if not already there.
     # ------------------------------------------------------------------------
-    def db_add_missing_topics(self, topics: List[str]) -> None:
+    def add_missing_topics(self, topics: List[str]) -> None:
         with self.db_session() as s:
             new_topics = [Topic(id=t) for t in topics
                           if (t,) not in s.query(Topic.id)]
@@ -317,6 +326,10 @@ class LearnApp(object):
     def db_setup(self, db: str) -> None:
 
         logger.info(f'Checking database "{db}":')
+        if not path.exists(db):
+            raise LearnException('Database does not exist. '
+                                 'Use "initdb-aprendizations" to create')
+
         engine = sa.create_engine(f'sqlite:///{db}', echo=False)
         self.Session = sa.orm.sessionmaker(bind=engine)
         try:
diff --git a/aprendizations/main.py b/aprendizations/main.py
index ee8a993..294168a 100644
--- a/aprendizations/main.py
+++ b/aprendizations/main.py
@@ -9,7 +9,7 @@ import sys
 from typing import Any, Dict
 
 # this project
-from .learnapp import LearnApp, DatabaseUnusableError
+from .learnapp import LearnApp, DatabaseUnusableError, LearnException
 from .serve import run_webserver
 from .tools import load_yaml
 from . import APP_NAME, APP_VERSION
@@ -160,7 +160,7 @@ def main():
     else:
         logging.info('SSL certificates loaded')
 
-    # --- start application
+    # --- start application --------------------------------------------------
     try:
         learnapp = LearnApp(courses=arg.courses,
                             prefix=arg.prefix,
@@ -178,13 +178,16 @@ def main():
               '--------------------------------------------------------------',
               sep='\n')
         sys.exit(1)
+    except LearnException as e:
+        logging.critical(e)
+        sys.exit(1)
     except Exception:
         logging.critical('Failed to start backend.')
         sys.exit(1)
     else:
         logging.info('LearnApp started')
 
-    # --- run webserver forever
+    # --- run webserver forever ----------------------------------------------
     run_webserver(app=learnapp, ssl=ssl_ctx, port=arg.port, debug=arg.debug)
 
 
diff --git a/demo/astronomy.yaml b/demo/astronomy.yaml
index 2f2a4a2..e1bf297 100644
--- a/demo/astronomy.yaml
+++ b/demo/astronomy.yaml
@@ -3,11 +3,11 @@
 # optional values applied to each topic, if undefined there
 # ----------------------------------------------------------------------------
 
-# defaults:
+# defaults:  FIXME not working
 #   file: questions.yaml
 #   shuffle_questions: true
 #   choose: 6
-#   max_tries: 2
+#   max_tries: 200
 #   forgetting_factor: 0.97
 #   min_level: 0.01
 #   append_wrong: true
--
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