v0.999992

Many changes as I tinkered during the holidays...

• HUP: A new surface and shot. It's a single use spring that also damages the tile it sits on when triggered.
• ROF: A variant of the PUF clouds that also inflicts ROT. This has a shot, though it is limited to + modes.
• Lobber Boss: A slow moving volcano spewing mobs and bullets. Only one chunk so far whilst it gets settled but...
• Boss chunks (levels 5, 6, 7) will no longer spawn the same boss twice in a level set. 
• The tutorial has been redesigned so it plays more like a regular level.
• The starting hut's gate now closes until the orb is collected. This makes the objective clearer. Reset is still available from the pause menu.
• Wallers now spawn an extra wall on death in + modes.
• Boxers now clear surfaces when spawning a box.
• Crumble ledges and walls can now be shot at to advance their timer after they have been triggered.
• Drop blocks now come in horizontal flavours as well.
• Some audio has been adjusted, eg: indestructible hits have been low passed filtered to remove the click they once had.
• Indestructible ledges now have similar hit effects to indestructible walls.
• More chunks.
• Many bug fixes, some critical.

The demo has also been updated to reflect the new features.

At this stage the bulk of the work left to do is level chunks and polish. At least twice as many chunks as are in the game now are needed to support the later levels.