Allow units for 'start_pos' (initial agent position)

columbus/env.py

@@ -504,6 +504,8 @@ class ColumbusConfigDefined(ColumbusEnv):
         super().__init__(
             observable=observable, fps=fps, env_seed=env_seed, **kw)
         self.entities_definitions = entities
+        self.start_pos = self.conv_unit(self.start_pos[0], target='em', axis='x'), self.conv_unit(
+            self.start_pos[1], target='em', axis='y')
 
     def is_unit(self, s):
         if type(s) in [int, float]:

configs/Example_Units.yaml

@@ -65,14 +65,14 @@ params:
           pos: [0.75em, 60px]
         - type: RectBarrier
           num: 1
-          width: 2ct
-          height: 3ct
+          width: 20 # defaults to rx (px scaled from x-axis)
+          height: 10 # defaults to ry (px scaled from y-axis)
           pos: [0.75em, 90px]
         - type: OnceReward
           reward: 100
           radius: 3ct
-          pos: [0.3, 0.8]
-      start_pos: [0.1, 0.21]
+          pos: [0.3, 0.8] # defaults to em
+      start_pos: [90ct, 20ct]
       default_collision_elasticity: 0.8
       start_score: 10
       speed_fac: 0.01