In events, conditions filter instances that meet some criteria. They appear to the left of the event. All conditions in an event must be met by at least one instance for the actions to run. The actions then only apply to the instances that met the conditions.
System conditions do not pick any instances: they are simply either true or false, unless they specifically reference an object, such as with Pick random instance.
There are three kinds of conditions: normal conditions, triggered conditions, and looping conditions. You can also create OR blocks which run if any condition is true, rather than all the conditions. See How events work for more information.
Adding and editing conditions
When you add a new event, you are taken through the process of adding the first condition for the event. This is described in more detail in the Event Sheet View entry.
You can add multiple conditions to an event block. To add another condition, right-click either an existing condition or the event margin and select Add another condition. All conditions must be met for the event to run, unless you set the event to be an OR block, in which case any condition can be true for the event to run. To set an OR block, right-click the event margin and select Make 'Or' block.
To edit a condition, double-click it. You can also right-click it and choose Replace or Delete.
Conditions can be inverted, which flips the thing they test. For example, the condition Monster is overlapping Player is true whenever a monster is touching the player. However, if inverted, it appears with a red invert icon and means Monster is not overlapping Player.
Not all conditions can be inverted (e.g. triggers can't be, because the event doesn't make sense inverted in that case).
It is possible to place a breakpoint on a condition, to pause execution when it is reached. For more information, see breakpoints.