diff --git a/py/20200221_experiment_scheduling.py b/py/20200221_experiment_scheduling.py
index e29f8be..e782ec5 100644
--- a/py/20200221_experiment_scheduling.py
+++ b/py/20200221_experiment_scheduling.py
@@ -9,26 +9,22 @@
 from pyschedule import Scenario, solvers, plotters, alt
 
 # the planning horizon has 
-s = Scenario('Prolific500', horizon=15)
+s = Scenario('Prolific500', horizon=60)
 
 session = s.Resource('Session', num=1)
 
 mmi = s.Task('MMI', length=3, delay_cost=1)
-nb = s.Task('NB',length=5, delay_cost=1)
-ds = s.Task('DS',length=5, delay_cost=1)
+games = s.Task('games',length=45, delay_cost=1, is_group=True)
 nasa_tlx = s.Task('NSA_TLX', length=1, delay_cost=1)
 
 # define the tasks that each subject must perform in first session
 mmi += alt(session)
-nb += alt(session)
-ds += alt(session)
+games += alt(session)
 nasa_tlx += alt(session)
 
 # add precedences
-s += mmi < nb 
-s += mmi < ds 
-s += ds < nasa_tlx
-s += nb < nasa_tlx
+s += mmi < games 
+s += games < nasa_tlx
 
 # compute and print session schedules
 solvers.mip.solve(s,msg=1)