bombs and level maps

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+
+Picking up bombs in the game seems simple enough... but the way they're
+implemented in the code isn't.
+
+Each level has:
+
+- bomb graphics in the map data
+- a list of bombs (indexed by 'coarse grid' coordinates)
+- a list of map changes that happen when a bomb is picked up (optional)
+- a subroutine that gets called on bomb pickup (optional)
+- a subroutine that only gets called when certain bombs are
+  picked up... but this isn't used in Jumpman Junior (probably
+  it's a leftover from original Jumpman)
+- another bomb-related list that I haven't figured out yet
+- a byte that tells the game how many points a bomb pickup is
+  worth... but it's set to $64 (100) on every level in the game.
+- a shape to draw to replace the bomb, when it's picked up. Likely
+  this is just a 4x4 blank square on most levels, but Figurits
+  Revenge probably has a girder here instead (I can't remember if
+  *every* bomb on that level causes a girder section to appear though)
+
+Coarse Grid Coordinates
+-----------------------
+
+Effectively, the level is split into an invisible 8x8 grid, and only one
+bomb can appear in each grid square. When a bomb is touched (detected
+by GTIA collision register), the bomb_pickup routine gets called. It
+turns the current player X and Y coordinates (in pixels/scanlines)
+into coarse grid coordinates basically by lopping off the lower-order
+bits. Since the Atari's display is larger than the visible portion,
+the outermost grid squares are actually off the screen. This means the
+grid is effectively more like 6x7 than 8x8. Each grid square can only
+contain one bomb, so there's a limit of 64 (or really 42) bombs per level.
+
+The coarse coordinates are combined into one byte, and this byte is
+searched for in the bomb list. When it's found, its position in the
+list is used as an index into the other two lists (the map changes list
+and the one I don't know what it's for yet). If the byte isn't found
+before the $FF that terminates the list, bomb_pickup returns (so no
+points are awarded and no bomb-picked-up sound is heard, and the bomb
+doesn't disappear... doesn't happen on any of the levels as far as I
+can remember though).