More noise!

Arenas feature now some blocks that can be destroyed by shooting at them: at first, that might seem useful to wander around more easily, but, on second thought, that also makes life easier to wors! In fact, they can destroy the blocks, too...
(Note: in the future, the blast marks on the ground might: a) stay as they are; b) go; c) be extended to affect also the vertical elements like walls. Option c) is the most unlikely.)

CHANGELOG

• Added destroyable blocks.
• Assigned [SPACE], [ENTER], [RETURN], [CONTROL], [SHIFT], [TAB] the shooting function.
• Touched up graphics.
• Added one arena.
• Updated/improved manual.
• Made other internal improvements/bugfixes.