https://koshinstudio.com/en/notes/ Development logs from building browser games and an iOS app, with measured numbers en https://koshinstudio.com/en/notes/danmaku-patterns/ https://koshinstudio.com/en/notes/danmaku-patterns/ Fri, 06 Nov 2026 15:00:00 GMT The exact math behind ring, aimed (odd vs even), rain, spiral and homing bullet-hell patterns, from a real danmaku game, with live demos. https://koshinstudio.com/en/notes/rank-verify-mismatch/ https://koshinstudio.com/en/notes/rank-verify-mismatch/ Fri, 06 Nov 2026 15:00:00 GMT Honest runs of a browser game stopped reaching the online leaderboard: two game values changed without updating the server that re-checks scores. The fix, and a test that compares both sides with the same seeds. https://koshinstudio.com/en/notes/tcg-lottery-app-compare/ https://koshinstudio.com/en/notes/tcg-lottery-app-compare/ Fri, 06 Nov 2026 15:00:00 GMT Five apps and sites that track Pokémon card and TCG lotteries, pre-orders and restocks at stores in Japan, compared on games, alerts, maps and price — by the developer of one of them, weak points included. https://koshinstudio.com/en/notes/swiftui-hit-area/ https://koshinstudio.com/en/notes/swiftui-hit-area/ Fri, 16 Oct 2026 15:00:00 GMT The “Won” and “Lost” buttons responded only on the text. Two earlier fixes (modifier order) did not work; I built the look inside a ButtonStyle and replaced six places. A mail-order article with coordinates had the same kind of root. https://koshinstudio.com/en/notes/icloud-overwrite/ https://koshinstudio.com/en/notes/icloud-overwrite/ Fri, 16 Oct 2026 15:00:00 GMT The iCloud sync function never checked whether data was newer and replaced everything. A fresh device with an empty state could overwrite another device’s 20 records with 1. I added update-time comparison and never overwrite with empty. https://koshinstudio.com/en/notes/test-ads/ https://koshinstudio.com/en/notes/test-ads/ Fri, 16 Oct 2026 15:00:00 GMT Before ads were served, 25 of 163 real-device checklist items could not be verified. In developer mode only, the app switches to Google’s test ad units. Prize names are read from one setting and never hard-coded, including in the checklist. https://koshinstudio.com/en/notes/negaeri-online/ https://koshinstudio.com/en/notes/negaeri-online/ Fri, 16 Oct 2026 15:00:00 GMT Online play without login. Moves are validated by the rules engine, the clock lives only on the server, a disconnect gets 30 seconds, tokens are signed with HMAC, and ratings use pre-match numbers. With real values from the server code. https://koshinstudio.com/en/notes/negaeri-balance/ https://koshinstudio.com/en/notes/negaeri-balance/ Fri, 16 Oct 2026 15:00:00 GMT A 6×6 board game where sandwiched pieces defect. Instead of guessing the numbers, I ran 40 to 100 AI-vs-AI games per rule. Flips per move went from 2% to 81%, removing the king guard ended games in 17 moves, and the first-move edge is still unsolved. https://koshinstudio.com/en/notes/tcg-store-matching/ https://koshinstudio.com/en/notes/tcg-store-matching/ Fri, 06 Nov 2026 15:00:00 GMT Four real cases where matching store names went wrong in a trading-card lottery app: spelling variants, a map lookup that returned Shizuoka, one entry page used by different stores, and one form for six products. https://koshinstudio.com/en/notes/crawl-monitoring/ https://koshinstudio.com/en/notes/crawl-monitoring/ Fri, 06 Nov 2026 15:00:00 GMT Seven records of counting and cutting misses while crawling and monitoring lottery and first-come sales: aggregator pagination, gaps in X monitoring, how coverage was measured, intervals vs delivery, and waiting-room pages. https://koshinstudio.com/en/notes/scheduled-jobs/ https://koshinstudio.com/en/notes/scheduled-jobs/ Fri, 06 Nov 2026 15:00:00 GMT Nine records from the jobs that run hourly and daily, and the server under them: moving from Cloud Functions to a VPS, a timeout fixed three times, checks that never ran, re-runs on every deploy, and secrets in logs. https://koshinstudio.com/en/notes/card-supplies-guide/ https://koshinstudio.com/en/notes/card-supplies-guide/ Thu, 15 Oct 2026 15:00:00 GMT What to check before buying Pokémon card sleeves, toploaders and deck boxes: standard vs small size, what 35pt means, and a buying checklist. Not a hands-on review; unverified points are listed. https://koshinstudio.com/en/notes/itms-91064/ https://koshinstudio.com/en/notes/itms-91064/ Wed, 07 Oct 2026 15:00:00 GMT An iOS build was rejected by Apple's automated review with ITMS-91064. NSPrivacyTracking was true while NSPrivacyTrackingDomains was an empty array. How it was fixed, and what was not verified. https://koshinstudio.com/en/notes/xcode152-sdk/ https://koshinstudio.com/en/notes/xcode152-sdk/ Thu, 08 Oct 2026 15:00:00 GMT On an old Mac stuck on Xcode 15.2, newer Firebase and AdMob SDKs fail to build. Which versions break, which I pinned (Firebase 11.4.0, AdMob 11.5.0), and why. https://koshinstudio.com/en/notes/torecadash-watchdog/ https://koshinstudio.com/en/notes/torecadash-watchdog/ Thu, 08 Oct 2026 15:00:00 GMT An iOS app was force-quit by the watchdog (0x8BADF00D). A SwiftUI computed property re-filtered and re-sorted 951 articles on the main thread every body evaluation. https://koshinstudio.com/en/notes/torecadash-ci/ https://koshinstudio.com/en/notes/torecadash-ci/ Thu, 08 Oct 2026 15:00:00 GMT New builds stopped appearing in TestFlight. My first diagnosis (“[ci skip] is blocking builds”) was wrong; the workflow built the iOS app on every commit. https://koshinstudio.com/en/notes/apple-signin/ https://koshinstudio.com/en/notes/apple-signin/ Thu, 08 Oct 2026 15:00:00 GMT Force-quitting the app made Firebase create a new anonymous account each launch: 17 of 19 users were throwaway. Cause: reading currentUser too early. https://koshinstudio.com/en/notes/logo-pop/ https://koshinstudio.com/en/notes/logo-pop/ Thu, 08 Oct 2026 15:00:00 GMT Burst particles appeared in the wrong place on high-DPI screens. A canvas with only inset:0 keeps its pixel size, so it was 2x larger in CSS on Retina. https://koshinstudio.com/en/notes/stopwatch-rank/ https://koshinstudio.com/en/notes/stopwatch-rank/ Thu, 08 Oct 2026 15:00:00 GMT Why I truncate to three decimals so coarse clocks get no advantage, how ties (a 1/333 chance) are broken, and how I counted KV writes on the free tier. https://koshinstudio.com/en/notes/anime-db/ https://koshinstudio.com/en/notes/anime-db/ Thu, 08 Oct 2026 15:00:00 GMT An anime quiz picks from about 6,000 titles. Where they came from, the criterion that cut 62.3% of 16,177, what remains, and the biases of the method. https://koshinstudio.com/en/notes/match-percent/ https://koshinstudio.com/en/notes/match-percent/ Thu, 08 Oct 2026 15:00:00 GMT An anime quiz’s match percentage used a different yardstick from its ranking. With the old display, 35 to 40% of 1,000 synthetic respondents saw a reversed top 3. https://koshinstudio.com/en/notes/result-screen/ https://koshinstudio.com/en/notes/result-screen/ Thu, 08 Oct 2026 15:00:00 GMT The anime quiz showed the same two streaming buttons for every title; about 29% were wrong. How I narrowed buttons by availability and fixed image problems. https://koshinstudio.com/en/notes/first-visit/ https://koshinstudio.com/en/notes/first-visit/ Thu, 08 Oct 2026 15:00:00 GMT A browser game title screen had six things to press. I made the first step one button, and fixed saves vanishing inside an iframe and play continuing in a hidden tab. https://koshinstudio.com/en/notes/qiita-post-interval/ https://koshinstudio.com/en/notes/qiita-post-interval/ Thu, 08 Oct 2026 15:00:00 GMT After publishing, a new Qiita account could not create the next article. Checking the editor every 5 minutes, two measurements gave about 30 minutes; one was lost. https://koshinstudio.com/en/notes/crazygames/ https://koshinstudio.com/en/notes/crazygames/ Thu, 08 Oct 2026 15:00:00 GMT A game portal rejected my game with only “overall quality below expectations.” I recorded what the reviewer saw, found four causes and fixed them by measuring. https://koshinstudio.com/en/notes/ascii-text/ https://koshinstudio.com/en/notes/ascii-text/ Thu, 08 Oct 2026 15:00:00 GMT One character broke in a game portal’s preview though the file bytes were correct. How I made the game immune without finding the cause. https://koshinstudio.com/en/notes/deploy-gotchas/ https://koshinstudio.com/en/notes/deploy-gotchas/ Thu, 08 Oct 2026 15:00:00 GMT Stale cache, breadcrumbs that multiplied each build, a symlink into my own environment, and local-only images: four deploy incidents on Cloudflare Pages. https://koshinstudio.com/en/notes/hosting-compare/ https://koshinstudio.com/en/notes/hosting-compare/ Thu, 08 Oct 2026 15:00:00 GMT Cloudflare Pages, Netlify, Vercel, GitHub Pages and Firebase Hosting compared by official terms (Oct 2026): ads allowed, free limits, file limits, config. https://koshinstudio.com/en/notes/comment-services/ https://koshinstudio.com/en/notes/comment-services/ Thu, 08 Oct 2026 15:00:00 GMT giscus, utterances, Disqus, Remark42, Cusdis, Staticman and Commento compared by official pages (Oct 2026): storage, ads and tracking, maintenance status. https://koshinstudio.com/en/notes/ios-sdk-compare/ https://koshinstudio.com/en/notes/ios-sdk-compare/ Thu, 08 Oct 2026 15:00:00 GMT AdMob, AppLovin MAX, LevelPlay, Firebase and Supabase compared by official pages (Oct 2026): payouts, privacy manifests, minimum Xcode, free tiers. https://koshinstudio.com/en/notes/claude-vs-gemini-api/ https://koshinstudio.com/en/notes/claude-vs-gemini-api/ Thu, 08 Oct 2026 15:00:00 GMT Claude and Gemini API compared by official pages (Oct 2026): small-model prices, web search cost and caps, spend limits, deprecation notice. https://koshinstudio.com/en/notes/webaudio/ https://koshinstudio.com/en/notes/webaudio/ Thu, 08 Oct 2026 15:00:00 GMT A browser game with no audio files: koto, taiko and gong synthesized with WebAudio. I could not listen, so I set volume by measuring waveform peaks. https://koshinstudio.com/en/notes/ranking-free-tier/ https://koshinstudio.com/en/notes/ranking-free-tier/ Thu, 08 Oct 2026 15:00:00 GMT A game ranking on Workers and D1: calls per play from 5 to 2, rows read from 421 to 221. Server-side rank counting and removing the preflight call. https://koshinstudio.com/en/notes/tcg-product-matching/ https://koshinstudio.com/en/notes/tcg-product-matching/ Fri, 06 Nov 2026 15:00:00 GMT Eight real failures in matching trading-card lottery articles to products: English vs katakana names, splitting 9-pack sets, products seeded from official catalogs, spreading typos, and leaked values. https://koshinstudio.com/en/notes/silent-failures/ https://koshinstudio.com/en/notes/silent-failures/ Fri, 06 Nov 2026 15:00:00 GMT Seven real cases where nothing raised an error yet real data was being dropped or never read: regexes, dates without a year, truncated AI answers, t.co relays, notice pages, swallowed try? failures, and fail-open. https://koshinstudio.com/en/notes/data-repair/ https://koshinstudio.com/en/notes/data-repair/ Fri, 06 Nov 2026 15:00:00 GMT Seven real lessons from repairing bad data: fixing the gate does not fix existing data, cleanup can hide entry bugs, a bulk job that hit everything, how duplicates were counted, and notifications that cannot be undone. https://koshinstudio.com/en/notes/app-store-review/ https://koshinstudio.com/en/notes/app-store-review/ Fri, 06 Nov 2026 15:00:00 GMT Records of an indie iOS app stuck in App Store review: the six items asked for in Guideline 2.1 Information Needed on the first submission, and four rejections including iPad screenshots. https://koshinstudio.com/en/notes/u2028/ https://koshinstudio.com/en/notes/u2028/ Thu, 08 Oct 2026 15:00:00 GMT Python splitlines() broke a JSONL file because 2 of 7,247 records contained U+2028 (LINE SEPARATOR). Why it happens and the one-line fix: split on the newline only. https://koshinstudio.com/en/notes/shindan12/ https://koshinstudio.com/en/notes/shindan12/ Thu, 08 Oct 2026 15:00:00 GMT A 50-question anime quiz now gives a result after 12. Measured with 1,000 synthetic respondents: the type mostly matches, but the single recommended title changes a lot. https://koshinstudio.com/en/notes/sushi-measure/ https://koshinstudio.com/en/notes/sushi-measure/ Thu, 08 Oct 2026 15:00:00 GMT Rebalancing a merge puzzle, I found my measurement had counted falling pieces. Three causes: a backward size ladder, a pit-shaped tub, and pieces tunneling the floor. https://koshinstudio.com/en/notes/adgap/ https://koshinstudio.com/en/notes/adgap/ Thu, 08 Oct 2026 15:00:00 GMT Why I replaced “one ad every 5 plays” with “7 minutes since the last ad” in a browser game, how it behaves, and what I still do not know. https://koshinstudio.com/en/notes/ai-cost-cutting/ https://koshinstudio.com/en/notes/ai-cost-cutting/ Fri, 06 Nov 2026 15:00:00 GMT Five records of cutting AI (Claude, Gemini), Firestore and crawling costs in an indie app: doubting the meter first, converting to yen, and counting where the money actually went. https://koshinstudio.com/en/notes/anago/ https://koshinstudio.com/en/notes/anago/ Thu, 08 Oct 2026 15:00:00 GMT I could never reach my puzzle’s last piece. Statistics from hundreds of auto-played games showed the real cause: everything was too big for the tub.