The reactor has 3 cores, each with a 30-segment status indicator.

One segment is indicated per Reactor clock count.

Once a core has reached "critical" condition (all 30 segments are indicated), it's indicator lamps will flash.

A "hit" on the core hatchway will open it so that the core can be reset and the reactor clock will be reset to that core's timeset.  A timer will close the core hatchway after the core has been reset.

There are 2 control pads that require a 3-touch password to expose a red "system reset" button.
A direct hit on the system reset button will reset all 3 cores.  The reactor clock will also be reset but it's interval will be shortened by 100.

Adjacent to each control pad is a light blue "core open" button.  Hitting the button will cause all "active" hatchways to be opened and a timing sequence started to close them.

In the "chute" between the core open buttons is a "maintenance reset" that will set the reactor clock back by 10 units.

When all 3 reactor cores reach "critical" level, you will have 30 seconds to reset any one of the cores or to expose and hit the system reset button.  These tasks become difficult because of the violent shaking caused by the failure of the reactor's structural features.  Failure to perform a reset will result in a core meltdown.

There is no "tilt" feature and no ball count.  Keep playing as long as you can avoid a "nuclear incident".