diff --git a/app.py b/app.py
index 3c25f8f..e60f9d1 100644
--- a/app.py
+++ b/app.py
@@ -30,7 +30,9 @@ pio.templates["plotly_light"].layout['yaxis']['zerolinecolor'] = 'lightgray'
   
 ELM = {
   'name': 'tempplot',
-  'filename': './data/20260420213656.txt',
+  'filedir': './data',
+  # 'filename': './data/20260420213656.txt',
+  'filename': None,
   'label_file_fmt': 'File: {filename}',
   'label_data_len_fmt': 'Data points: {num:,} (rendered) / {numa:,} (total)',
   'label_data_temp_fmt': 'Temperature = [{min:.1f}, {max:.1f}] K',
@@ -94,79 +96,83 @@ async def pick_file() -> None:
     ELM['label_file'].set_text(ELM['label_file_fmt'].format(filename=os.path.basename(filename)))
 
 def get_data(filename=ELM['filename']):
-  data = np.genfromtxt(fname=filename, skip_header=1)
+  data = None
+  if filename is not None and os.path.isfile(filename):
+    data = np.genfromtxt(fname=filename, skip_header=1)
 
-  if len(data) > 0 and len(data[0]) > 6:
-    names = ['time', 'ts', 'ta', 'tb', 'tc', 'td', 'hp', 'hl']
-  else:
-    names = ['time', 'ts', 'ta', 'tb', 'hp', 'hl']
+    if len(data) > 0 and len(data[0]) > 6:
+      names = ['time', 'ts', 'ta', 'tb', 'tc', 'td', 'hp', 'hl']
+    else:
+      names = ['time', 'ts', 'ta', 'tb', 'hp', 'hl']
 
-  data = np.genfromtxt(
-    fname=filename, dtype=None, skip_header=1, converters={
-      0: lambda x: datetime.datetime.strptime(x, '%Y%m%d%H%M%S')},
-    names=names, encoding='utf-8'
-  )
+    data = np.genfromtxt(
+      fname=filename, dtype=None, skip_header=1, converters={
+        0: lambda x: datetime.datetime.strptime(x, '%Y%m%d%H%M%S')},
+      names=names, encoding='utf-8'
+    )
   return data
 
 def update_data():
-  if not app.storage.user['timer'] or time.time() - ELM['update_last'] > ELM['update_timeout']:
+  if not app.storage.user['timer'] \
+     or time.time() - ELM['update_last'] > ELM['update_timeout']:
     ELM['update_busy'] = True
     filename=ELM['filename']
     data_all = get_data(filename)
     data = data_all
 
-    # time_range = ELM['number_time_range'].value
-    time_range = app.storage.user['time_range']
-    if time_range is not None and time_range > 0:
-      # delta = datetime.datetime.now() - data['time']
-      delta = data['time'][-1] - data['time']
-      data = data[np.where(delta <= datetime.timedelta(hours=time_range))]
-    print(datetime.datetime.now(), filename, data_all.shape, data.shape)
-    ELM['label_data_len'].set_text(ELM['label_data_len_fmt'].format(
-      num=len(data), numa=len(data_all)))
-    
-    if len(data) > 0:
-      if len(data[0]) > 6:
-        ELM['label_data_temp'].set_text(ELM['label_data_temp_fmt'].format(
-          min=np.min([data['ts'], data['ta'], data['tb'], data['tc'], data['td']]),
-          max=np.max([data['ts'], data['ta'], data['tb'], data['tc'], data['td']])))
-      else:
-        ELM['label_data_temp'].set_text(ELM['label_data_temp_fmt'].format(
-          min=np.min([data['ts'], data['ta'], data['tb']]),
-          max=np.max([data['ts'], data['ta'], data['tb']])))
-    ELM['label_data_heat'].set_text(ELM['label_data_heat_fmt'].format(
-      min=np.min(data['hp']), max=np.max(data['hp'])))
+    if data is not None:
+      # time_range = ELM['number_time_range'].value
+      time_range = app.storage.user['time_range']
+      if time_range is not None and time_range > 0:
+        # delta = datetime.datetime.now() - data['time']
+        delta = data['time'][-1] - data['time']
+        data = data[np.where(delta <= datetime.timedelta(hours=time_range))]
+      print(datetime.datetime.now(), filename, data_all.shape, data.shape)
+      ELM['label_data_len'].set_text(ELM['label_data_len_fmt'].format(
+        num=len(data), numa=len(data_all)))
 
-    ELM['fig'].data = []
-    ELM['plot'].visible = False
-    ELM['plot'].update()
+      if len(data) > 0:
+        if len(data[0]) > 6:
+          ELM['label_data_temp'].set_text(ELM['label_data_temp_fmt'].format(
+            min=np.min([data['ts'], data['ta'], data['tb'], data['tc'], data['td']]),
+            max=np.max([data['ts'], data['ta'], data['tb'], data['tc'], data['td']])))
+        else:
+          ELM['label_data_temp'].set_text(ELM['label_data_temp_fmt'].format(
+            min=np.min([data['ts'], data['ta'], data['tb']]),
+            max=np.max([data['ts'], data['ta'], data['tb']])))
+      ELM['label_data_heat'].set_text(ELM['label_data_heat_fmt'].format(
+        min=np.min(data['hp']), max=np.max(data['hp'])))
 
-    # mode='lines+markers' too heavy
-    ELM['fig'].add_trace(pgo.Scatter(
-      **np2pgo(data['time'], data['ts'], 'Setp'), mode='lines', legendgroup=None))
-    ELM['fig'].add_trace(pgo.Scatter(
-      **np2pgo(data['time'], data['ta'], 'Temp A'), mode='lines', legendgroup=None))
-    ELM['fig'].add_trace(pgo.Scatter(
-      **np2pgo(data['time'], data['tb'], 'Temp B'), mode='lines', legendgroup=None))
-    if len(data) > 0 and len(data[0]) > 6:
+      ELM['fig'].data = []
+      ELM['plot'].visible = False
+      ELM['plot'].update()
+
+      # mode='lines+markers' too heavy
       ELM['fig'].add_trace(pgo.Scatter(
-        **np2pgo(data['time'], data['tc'], 'Temp C'), mode='lines', legendgroup=None))
+        **np2pgo(data['time'], data['ts'], 'Setp'), mode='lines', legendgroup=None))
       ELM['fig'].add_trace(pgo.Scatter(
-        **np2pgo(data['time'], data['td'], 'Temp D'), mode='lines', legendgroup=None))
+        **np2pgo(data['time'], data['ta'], 'Temp A'), mode='lines', legendgroup=None))
+      ELM['fig'].add_trace(pgo.Scatter(
+        **np2pgo(data['time'], data['tb'], 'Temp B'), mode='lines', legendgroup=None))
+      if len(data) > 0 and len(data[0]) > 6:
+        ELM['fig'].add_trace(pgo.Scatter(
+          **np2pgo(data['time'], data['tc'], 'Temp C'), mode='lines', legendgroup=None))
+        ELM['fig'].add_trace(pgo.Scatter(
+          **np2pgo(data['time'], data['td'], 'Temp D'), mode='lines', legendgroup=None))
 
-    ELM['fig'].add_trace(pgo.Scatter(
-      **np2pgo(data['time'], data['hp'], 'Heat'), mode='lines',
-      legendgroup=None), row=2, col=1)
+      ELM['fig'].add_trace(pgo.Scatter(
+        **np2pgo(data['time'], data['hp'], 'Heat'), mode='lines',
+        legendgroup=None), row=2, col=1)
 
-    ELM['plot'].visible = True
-    ELM['plot'].update()
+      ELM['plot'].visible = True
+      ELM['plot'].update()
 
-    ELM['update_last'] = time.time()
+      ELM['update_last'] = time.time()
 
-    ELM['label_update_last'].set_text(
-      ELM['label_update_last_fmt'].format(
-        last=datetime.datetime.fromtimestamp(
-          ELM['update_last']).strftime("%Y-%m-%dT%H:%M:%S.%f")))
+      ELM['label_update_last'].set_text(
+        ELM['label_update_last_fmt'].format(
+          last=datetime.datetime.fromtimestamp(
+            ELM['update_last']).strftime("%Y-%m-%dT%H:%M:%S.%f")))
     
 def update_fig():
   ELM['fig'].update_yaxes(
@@ -221,8 +227,10 @@ def index():
     ).bind_value(app.storage.user, 'dark_mode').props('icon="dark_mode"')
 
   with ui.row():
-    ELM['label_file'] = ui.label(
-      ELM['label_file_fmt'].format(filename=os.path.basename(ELM['filename'])))
+    filename = None
+    if ELM['filename'] is not None:
+      filename = os.path.basename(ELM['filename'])
+    ELM['label_file'] = ui.label(ELM['label_file_fmt'].format(filename=filename))
     ELM['label_data_len'] = ui.label(ELM['label_data_len_fmt'].format(num=0, numa=0))
     ELM['label_data_temp'] = ui.label(ELM['label_data_temp_fmt'].format(min=0, max=0))
     ELM['label_data_heat'] = ui.label(ELM['label_data_heat_fmt'].format(min=0, max=0))