# UI Renderer

## Current state

No UI primitives exist. The framebuffer is currently filled by the game world only
(`render_viewport` in `game.rs`: tile pass + entity sprite pass). `pixelhelper.rs` has
low-level pixel/blit helpers but nothing higher-level.

## Goal

Draw common roguelike UI elements (panels, borders, HUD bars, etc.) procedurally into the
`u8` framebuffer, composited on top of the game world.

## Design notes

The virtual resolution is 320×240, so UI layout should be designed in those pixel units.

Likely primitives needed (built on top of `pixelhelper.rs`):

- `fill_rect(frame, x, y, w, h, color)` — solid filled rectangle
- `draw_rect(frame, x, y, w, h, color)` — 1-pixel border rectangle
- `draw_border_box(frame, x, y, w, h, tileset)` — box drawn with corner/edge tiles from
  a tileset (classic roguelike panel look)
- `draw_hbar(frame, x, y, w, value, max, fg, bg)` — horizontal progress/HP bar

Panels are typically fixed regions of the screen (e.g. a status bar at the bottom 40px,
a message log on the right). Hard-coding these regions first is fine; extract to a layout
system only if needed.

The UI layer draws after the world layer so it always appears on top. Draw order within
the UI should be back-to-front (backgrounds before text).

## Open questions

- Tileset-based borders vs. line-drawing: which look are we going for?
- Does the message log need scrolling? Probably not at first.