More around design documents, add save design doc

design/design.md

@@ -0,0 +1,79 @@
+# Premise
+
+- Evil source at bottom of playable map
+- Evil is surging upwards
+- Player is the one tasked with going to the bottom and destroying evil source
+- Very long way to bottom
+- Going deeper = main source progression
+- Barriers to going deeper, gotta craft gear, etc. to be able to go deeper
+- Tower defense elements, have to craft and set up defensive structures
+
+# Details
+
+## Timing
+Timing is tick based.
+Every frame is considered a tick.
+The game is locked at 60 fps to simplify implementation.
+
+## Scale
+Player character is slightly below 1.5 m height.
+1 meter = 2 blocks.
+1 block = 0.5 meters.
+Player character is about 3 blocks high. (slightly less so they fit comfortably)
+
+## Map Size
+
+World is roughly 100,000x100,000 blocks large.
+I've done some measurements and I believe it's large enough that it should convey
+the scale of digging very deep, which is what the game is about.
+Layer below 30 km is the mantle (after which the game is named).
+The evil source is at about 35 km.
+The final goal is the evil source, so player is expected to mine about 35 km deep to beat the game.
+1 meter = two tiles. 35 km = 70,000 tiles deep.
+There could be some post-endgame content from 35-40 kms deep.
+Very unbreakable bottom or lava lake or whatever is at 80,000 blocks (40 km) deep.
+
+## Biomes
+Only a few surface biomes
+- At center is forest biome
+- On one side:
+  - Jungle
+  - Desert
+- On other side:
+  - Longer stretch of forest biome than other side
+  - Ice biome
+
+All other biome variety should come from going deeper.
+Progressively more difficult variants of each biome as you go down.
+30 km is mantle level, at which point no ice or sand or such reaches.
+It's all mantle level specific biomes all the way horizontally.
+
+## Number of stuff
+
+- Up to 1000 tiles (1024*1024 tile sprite sheet)
+  - At least 100 ore types
+  - At least 50 stone types
+  - Maybe background tiles and other stuff, like different break overlay animations
+
+
+# Multiplayer
+
+Multiplayer adds a lot of complexity, so I'm going to develop the prototype of the game without
+any multiplayer support.
+But if people like the general idea, they can help create a multiplayer version eventually.
+
+# Crafting
+
+- You need a workstation to be able to craft anything.
+  This incentivizes building bases and retreating to them, instead of the "nomad"
+  lifetyle many games of this kind allow.
+
+- Most stations don't have inventory items that can be pre-crafted and placed.
+  Instead, they have to be constructed on the spot, taking construction time.
+  This discourages building makeshift crafting areas in the middle of nowhere.
+
+# Supported platforms
+- Windows
+- Linux
+
+Other platforms can be supported if community helps support them.

design/ideas.md

@@ -0,0 +1,15 @@
+Various random ideas that aren't (yet) part of the design
+
+- Character is 1.5 blocks tall
+- Can crawl to fit inside 1 block tall gaps
+
+
+- Multiple tile layers.
+    - Back layer
+    - Wall layer
+    - Ore/misc insert layer
+
+- No world hopping.
+  Characters are worlds are linked together, like in Minecraft.
+
+- No respawn after quit&save. Player character continues where it left off.

design/save.md

@@ -0,0 +1,13 @@
+Game has different worlds you can generate.
+Each world has its own folder.
+Each folder has:
+    - Player file (player.dat)
+    - Subfolder for regions (regions/)
+
+Each region subfolder has:
+r.x.y.dat files for each chunk, where x and y are the region coordinates.
+
+# Regions
+A region stores multiple chunks in a single file for more optimized storage.
+Current plan is to store 8 chunks in a region, in other words, 1024*1024 blocks.
+Around one million blocks, compressed with zstd compression.