Problem Solving & Design B+

Domain logic is cleanly separated from UI, validation is thorough, and the leaderboard correctly handles ties with shared ranks.

• +Tied players share the same rank number rather than receiving arbitrary sequential ranks, matching real scoring conventions.
• +Session data entering from localStorage is validated field-by-field through normalizeSession, so corrupt or tampered storage cannot crash the app.
• +The winner banner correctly returns an empty array when no rounds have been played, avoiding a misleading zero-score winner declaration.

Completeness A

All brief-required features are fully implemented, from session creation through past-session history review.

• +The two-step end-game confirm with auto-disarm after 4 seconds prevents accidental session termination while keeping the flow smooth.
• +Past sessions are rendered in a read-only table showing every round's deltas plus a totals row, exactly as the brief requires.
• +The history list shows an empty-state message when no finished sessions exist yet.

Technical Craft A

The codebase demonstrates strong TypeScript discipline, a well-structured CSS design system, accessible markup, and meaningful automated tests covering core domain logic.

• +CSS custom properties define the entire colour and spacing system in one place, with a light-mode override block that swaps every token coherently.
• +The score pop animation respects prefers-reduced-motion by disabling all animations and transitions for users who need it.
• +Storage write failures surface a visible banner on every mutation path via a single persist() call that checks the save result.
• +Automated tests cover tie-rank sharing, decimal truncation, blank-input coercion, and normalizeSession rejection cases.
• -The active-session grid switches to two columns at 760 px but has no intermediate breakpoint, so on mid-range tablets the round-input column can feel cramped before the split kicks in.
• -localStorage is read once at boot but the app never limits the stored array to the last 5 sessions — it grows unboundedly, which could eventually hit quota on devices with many sessions.