Finally another preview is ready!

This is what it includes:
* quickstart guide
* intro
* manual
* full zones 1 and 4
* placeholders for zones 2 and 3
* crippled zone 5
* placeholder for outro

This is what it does not include:
* full zone 5
* outro

This is what is still to be done:
* making zones 2 and 3;
* exploiting the remaining 512 bytes VIC-II bank space for zones 4 and 5;
* writing outro music.

The changelog below provides the detailed list of changes since the previous preview; highlights:
* completed zone 1;
* added 8 new baddies;
* added saving of game progress;
* made many bugfixes and optimizations.

Preview 6 (12.5.2023)
* Added 8 new baddies (they are 16 in all now).
* Re-added stopping of food/drinks generation after Zampo starves (found a way to do it basically at no cost).
* Saved 234 to 244 bytes (depending on the zone) by reorganizing a bit the memory map once again.
* Saved 257 to 266 bytes (depending on the zone) by moving the zone-complete transition from the zone program to a separate program.
* Saved a sprite page by reworking the graphics and the logic of the baddies explosion.
* Made a few optimizations.
* Made various other minor improvements.
* Fixed a rare endless wait (due to lack of CPU cycles).
* Fixed the portals graphics update and a CPU load peak (which might even cause a frame skip) in the FUN PARK zone (a routine used the wrong condition code in a branch, so the portals graphics update was triggered also when it should not have been).
* Fixed the handling of collisions against baddies when Zampo is being relocated (if Zampo had been in PIG-OF-STEEL mode, collisions were detected and baddies were killed).
* Fixed the handling of collisions against baddies when the GOLD mode is starting (due to the initial flashing of Zampo's skin, collisions could be detected).
* Fixed the handling of collisions against baddies when the distance from the checkpoint is very large (the quick relocation of Zampo to the checkpoint would cause the immediate disappearance of the baddie, so collisions would not longer be detected until the same or another baddie re-appeared on the screen, thus leaving the collision flag set and causing repeated collision detections).
* Fixed the handling of collisions against slides in the FUN PARK zone (Zampo could get stuck due to a tile index constant being off by one and another tile index constant indicating the opposite tile).
* Fixed the teleporting of Zampo from the left border of the bottommost portal of the FUN PARK zone (he was taken to another portal's destination due to a coordinate constant being off by one).
* Fixed the turbofart flame at the end of the zone-complete transition (it was shown for 2 frames instead of 1).
* Fixed the lighting property of a FUN PARK zone tile.
* Worked on the FUN PARK zone map: made it 64 pixels taller (now it is 2048x912 pixels); completed the layout; added gameplay features; improved the graphics; moved the exit point to a better (and recognizeable) place; fixed some tiles.
* Worked on the CLIFFS zone map: made it 16 pixels taller (now it is 2048x944 pixels); extended the underground part.
* Worked on the FORTRESS zone map: made it 16 pixels taller (now it is 2048x896 pixels); extended the underground part; touched it up in a few places.
* Worked on the frontend: restricted the selectable zones to the first one and any other reached previously; made the outro item activate only upon game completion (so, when the game has not been completed, it cannot be selected and only its silhouette is visible); added auto-selection of the joystick item when [UP] or [DOWN] is pressed; added zones numbers in front of the zones names; made it smaller.
* Worked on the preamble: made it smaller.
* Worked on the documentation: extended/improved/fixed quickstart guide and manual.
* Worked on EasyFlash features: embedded and used EasyAPI to save the game progress permanently and thus have the frontend enable the zones/outro accordingly; ensured the LED is on/off when the cartridge is / is not in use; added cartridge name.