Thanks for buying it, and thanks for asking — that's a fair complaint. The Spectrum has eight colours and no room for icons, so everything had to be said with a colour, a texture or a tiny mark in the corner of a tile. Here's the whole vocabulary.
First, the plain ground. A tile has three lives, and its colour is how many are left: white = 3, yellow = 2, red = 1, black = gone. A worn tile also loses a bite out of its corners — one bite at 2, two at 1. The bright/dim alternation is just the chequerboard pattern; it means nothing about wear. And the little arrow in the bottom-right corner means "one more crossing and this square is gone" — step there and you can still stand, you just can't come back.
The anvil — solid magenta square. Land on it and it repairs the four squares directly north, south, east and west of it: each gains one life back. It works once, then it's spent. It never takes a tile above three lives, and it never brings back a hole — what has collapsed stays collapsed. Landing on it is the whole point; crossing over it does nothing.
The granite — solid cyan square. It never wears. Cross it as often as you like. It's the only permanent ground you're given for free, so in most levels the granite is the skeleton your route hangs off.
The clock — an hourglass in the top-left corner of a tile (from level 25 on). That tile rots on its own: it loses one life every three moves whether you touch it or not. The counter in the status bar marked ROT tells you how many moves until the next tick. When the tick is on your very next move, the hourglass turns red and flashes — that's your last warning. An anvil can hold a rotting tile up for one more round, because the clock ticks after your move, not before.
The road — a white brick texture (levels 65–69). These levels invert the game: the board starts half missing, and every tile you leave while it's still alive turns to brick and never wears again. You're building a road instead of burning bridges. The catch: a fragile tile dies the moment you step on it, so it's already dead when you leave — you can only pave ground that had something left in it.
Two more things that aren't obvious: your piece is the blue one; the enemies are black silhouettes on their own squares. And the gate (green) doesn't change appearance when it opens — the MEALS/EAT counter turns green instead. That's the only signal, and it's easy to miss.
One honest wart: on the Spectrum a spent anvil still looks magenta, so it lies to you after you've used it. On the PC version it goes back to looking like ordinary ground. That's an oversight rather than a design choice, and I'll fix it in the next build.
Hope that unlocks it. If any specific level is being stubborn, tell me the number and I'll tell you what it's testing