Enemy shooting occurs when the player is within a certain range and direction, with  cooldown time. 

I've added a suitable explosion. The parallax has been implemented to work in all four directions.

The map is generated using 20 stacked lists, each specifies a content horizontally.

The list items are read under iteration to determine their coordinates. The coordinates are used when generating sprite instances,  which are later added to designated sprite groups.

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 HORIZONTAL TILING -  (current)

1st list - parallax layer  - ->

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2nd list - parallax layer   -->

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3rd list -  ground  -->

 start                                                    finish (very long list)

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VERTICAL TILING - (easier to manage)

                                       list number

FIRST ITEM           | 1  | 2  | 3  | 4 | 5  | 6  | 7  | 8  | 9 | 10   |    <---parallax layer 2

SECOND ITEM   | 1  | 2  | 3  | 4 | 5  | 6  | 7  | 8  | 9 | 10  |     <---parallax layer 1

THIRD ITEM        | 1  | 2  | 3  | 4 | 5  | 6  | 7  | 8  | 9 | 10  |     <---ground

                                      start                                                     finish