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Phase 5: Tetris Implementation Plan¶

For agentic workers: REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development or superpowers:executing-plans.

Goal: Ship examples/tetris/ — playable Tetris compiled with li, SDL2 window, keyboard input, 60 FPS loop.

Architecture: Game logic in li with fixed-size board types; thin SDL2 extern layer; no heap allocator required.

Depends on: Phase 4
Blocks: Nothing (v1 milestone complete)

Constants (compile-time shaped)¶

const BOARD_W = 10
const BOARD_H = 20
const CELL_PX = 24

type
  Color = enum
    Empty, Cyan, Yellow, Purple, Green, Red, Blue, Orange

  Cell = object
    color: Color

  Board = array[BOARD_H, array[BOARD_W, Cell]]
  PieceKind = enum
    I, O, T, S, Z, J, L

Board type errors (wrong row/col in indexing) must fail at compile time when indices are literals.

Task 1: SDL2 extern bindings¶

Files: - Create: examples/tetris/sdl2.li (extern block) - Create: examples/tetris/build.sh (optional wrapper with pkg-config sdl2)

Extern: SDL_Init, SDL_CreateWindow, SDL_CreateRenderer, SDL_SetRenderDrawColor, SDL_RenderClear, SDL_RenderFillRect, SDL_RenderPresent, SDL_PollEvent, SDL_Quit
Event struct as opaque pointer + field accessors OR minimal POD matching SDL layout (document choice)

Task 2: Board + pieces¶

Files: - Create: examples/tetris/board.li - Create: examples/tetris/pieces.li

new_board() -> Board all Empty
Tetromino shapes as array[4, array[2, int]] offsets per rotation
can_place(board, piece, ox, oy) -> bool
lock_piece(board, piece, ox, oy) mutates board

Task 3: Game loop¶

Files: - Create: examples/tetris/game.li - Create: examples/tetris/main.li

proc run() raises IO
Gravity tick every N frames
Line clear: scan row, shift down
Game over when spawn blocked

Task 4: Input¶

Left/Right/Down arrows, Up rotates, Space hard drop
Map SDL keycodes in handle_event

Task 5: Render¶

Draw grid: filled rects per non-Empty cell
Draw active piece
Simple border

Task 6: Build + release¶

lic build examples/tetris/main.li -o tetris --release \
  $(pkg-config --libs --cflags sdl2)

60 FPS stable on M-series Mac
No leaks/crashes over 10-minute play session

Phase 5 exit gate (project milestone)¶

Playable Tetris binary
lic check catches wrong board dimensions in test fixture
Master plan tracker updated

Post-milestone demo script¶

lic check examples/tetris/main.li
lic build examples/tetris/main.li -o tetris --release
./tetris