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+# lockstep artillery - build roadmap
+
+## phase 1: foundation
+
+- [ ] set up build.zig with raylib-zig dependency
+- [ ] create fixed-point math module (Fixed struct, add/sub/mul/div)
+- [ ] create trig lookup tables (sin/cos at comptime)
+- [ ] basic window opens with raylib
+
+## phase 2: single-player simulation
+
+- [ ] define GameState, Player, Projectile structs
+- [ ] terrain generation (random jagged line)
+- [ ] cannon aiming (angle adjustment with keys)
+- [ ] power adjustment
+- [ ] fire projectile
+- [ ] projectile physics (gravity, movement)
+- [ ] terrain collision detection
+- [ ] player hit detection
+- [ ] turn switching after shot resolves
+
+## phase 3: rendering
+
+- [ ] draw terrain as connected line segments
+- [ ] draw players as geometric shapes
+- [ ] draw cannon angle indicator
+- [ ] draw power meter
+- [ ] draw projectile with trail (last N positions)
+- [ ] implement bloom shader (blur.fs)
+- [ ] render-to-texture pipeline for glow effect
+- [ ] explosion effect (expanding circle)
+
+## phase 4: local two-player
+
+- [ ] split keyboard input (player 1: wasd+space, player 2: arrows+enter)
+- [ ] verify determinism by running two simulations side-by-side
+- [ ] add checksum verification
+
+## phase 5: networking
+
+- [ ] UDP socket wrapper (bind, send, receive)
+- [ ] define packet format (INPUT, SYNC, PING, PONG)
+- [ ] host mode: listen for connection, send initial SYNC
+- [ ] guest mode: connect, receive SYNC, start simulation
+- [ ] input exchange each frame
+- [ ] handle packet loss (resend on timeout)
+- [ ] checksum exchange and desync detection
+- [ ] latency display
+
+## phase 6: polish
+
+- [ ] wind indicator
+- [ ] health bars
+- [ ] win/lose screen
+- [ ] rematch option
+- [ ] sound effects (optional, breaks no-dependency purity)
+
+## known pitfalls to watch
+
+- [ ] don't use floats in simulation
+- [ ] don't iterate hashmaps
+- [ ] don't use @sin/@cos - use lookup tables
+- [ ] always process inputs in same order (player 0 then player 1)
+- [ ] serialize terrain heights as fixed-point, not float
+
+## stretch goals
+
+- [ ] destructible terrain (explosion removes pixels)
+- [ ] multiple weapon types
+- [ ] rollback netcode (predict, rewind, replay on correction)
+- [ ] replay file save/load
+- [ ] web build via emscripten