1.2.5 - additional staircase hint

I mentioned in the 1.2.4 devlog earlier today trying to make navigating the stairs a little clearer, and this change is another tweak in that direction. As you can see, between 1.2.3 and 1.2.5, I have:

• Added 'floor' tiles to the top landing to hint that there are squares one can reach there,
• Modified the bottom tile of the stairs downwards to suggest some depth and make clearer the distinction between the center section and the edge sections, and
• Added two more unreachable sprites at the top of the stairs, suggesting to the player that (again) there is something worth investigating there.

It's odd, the things that seem obvious to myself and don't get across in the game, but I suppose it makes a bit of sense - people are very used to staircases that travel in helices - climb up one side, climb up further the other - but in this case the upwards section is in the middle and both sides go back down.

Which is difficult to convey at in 8x8 tiles. So ... hopefully this helps.