codegirl.games-hugo/content/posts/td-odin-week-4.md

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title	description	date	type	series	series_order	languages	tags
Week 4: Tests, refactors, and data tables	Fourth week on the Odin tower defense prototype: splitting tower placement, table-driven defs, first tests, and undoing a nested world refactor.	2026-06-29	devlog	tower-defense-prototype	5	odin	odin tower-defense devlog

Week four on the Odin prototype. Week three shipped fullscreen, three tower types, enemy variety, and splash damage. This week was quieter on features and heavier on structure: splitting files, pushing logic into data tables, and writing my first tests.

What I built

Split tower logic. tower.odin had grown to handle combat, stats, rendering, and placement. I pulled placement into tower_placement.odin: footprint checks, overlap tests, try_place_tower, ghost preview. Combat and archetypes stay in tower.odin. Placement is geometry; combat is timing and targeting. Keeping them separate made both files easier to navigate.

Data tables over switch statements. Several get_* functions became lookup tables:

• TILE_COLORS replaced a tile_color switch
• ENEMY_DEF replaced per-kind switch logic with base stats, per-wave scaling, draw radius, and gold reward in one row per enemy
• Tower archetypes dropped a redundant kind field and gained a color column for rendering

Tweaking tank gold from 5 to 10 or archer cost became a one-line edit instead of hunting through switch arms.

Constants consolidation. UI layout lived in helper functions that recalculated button rectangles every frame. Moved to constants.odin: ARCHER_BUTTON_RECT, START_WAVE_BUTTON_RECT, STARTING_GOLD, STARTING_BASE_HEALTH, overlay colors, control bar dimensions. controls.odin got shorter and the layout stopped drifting.

First tests. Added math2d_test.odin (distance, move_toward) and wave_test.odin (start wave, clear wave, recipe progression). Small suite, but it caught a wave recipe memory leak during gold rebalancing: the kind of bug I'd fixed once by hand and reintroduced during a refactor.

Economy pass. Gold rewards moved into enemy definitions. Tank kills pay more than grunts. Tower costs live in archetype rows. Balanced enough to play-test without obvious snowball or stall.

World struct simplified. Flattened base_health and map init into cleaner helpers. Started the week by reverting the nested Economy / Combat / Wave sub-structs from week three, back to a flat World with direct field access.

What worked

• Splitting placement from combat scaled better as tower logic grew
• Table-driven defs made adding and tuning enemy/tower stats mostly data changes
• Tests paid for themselves immediately on wave spawner edge cases
• Flat World struct was easier to reason about than nested sub-structs for a game this size

What broke

• Nested world refactor, reverted. Week three split World into Economy, Combat, and Wave sub-structs. Looked clean on paper. Every system suddenly needed world.combat.enemies instead of world.enemies, accessors multiplied, and nothing got simpler. Reverted on June 27. Don't refactor structure until the current shape is actually hurting you, and wait until you have tests.

• Test cleanup is manual. Odin tests that allocate dynamic arrays need explicit defer delete. Forgot once; leak showed up in the test runner, not the game.

Repo snapshot

June 27–29 touched 14 files, ~490 net lines. New modules: tower_placement.odin, math2d_test.odin, wave_test.odin. Three towers, three enemies, wave recipes, upgrades, splash damage, fullscreen, end screens, plus a test suite to build on.

Next: pathfinding, more tower shop wiring, ice slow polish, and whatever breaks once I add a fourth tower type.