Problem Solving & Design 100

The design is clean, visually coherent, and responsive; it solves the stated problem with encouraging visual feedback (emojis, milestone styling, color changes) and intuitive daily-task flow.

• +Visual hierarchy and typography are polished: clear h1 header, habit name prominence, streak numbers bold and large, emoji indicators at multiple scales.
• +Milestone detection works: cards glow with gold border at 7/30/100 day streaks; emoji progression (🌱→🔥→⭐→💎→🏆) reinforces motivation visually.
• +Responsive design: flexbox layout adapts to mobile and desktop; input form stacks well; habit cards wrap actions gracefully on narrow viewports.
• +Semantic HTML and accessibility signals: form has proper labels via placeholder and title attributes; buttons have clear text or titles; color is not the only indicator (emojis + text).
• +UX flow is intuitive: clear "Mark today done" button state toggles to "Done today ✓"; reset and delete prompt for confirmation to prevent accidents.

Completeness 100

All required features present and functional: habits add/delete, daily completion logging, streak calculation, 14-day calendar view, reset capability, and localStorage persistence all work end-to-end.

• +All core features listed in brief are implemented and wired into the UI: add, log, streak display, calendar, reset, and delete.
• +Streak calculation logic correctly handles edge cases: distinguishes between zero streak and active streaks, accounts for today vs yesterday.
• +localStorage persistence works with error handling; empty state displays correctly when no habits exist.
• +14-day calendar grid renders with visual distinction between completed days, today, and missed days.
• +Input validation: form requires non-empty habit names (HTML5 required + trim check); max 60 chars enforced.

Technical Craft 95

Solid architecture with clear separation of concerns, robust state management, and attention to detail; minor code-organization opportunities but no functional or security flaws.

• +State management is clean: single source of truth in habits array; save and load are explicit; render function is called consistently after mutations.
• +Streak calculation is mathematically correct: handles the "today or yesterday" start condition; avoids off-by-one errors common in streak logic.
• +Defensive coding: try-catch on localStorage parse; fallback UUID generation for older browsers (crypto.randomUUID or Date.now); confirmations prevent accidental destructive actions.
• +DOM manipulation is efficient: template cloning and reuse; minimal direct HTML string generation; event listeners attached only where needed.
• +Date handling is solid: dateKey and daysAgoKey functions abstract date logic; consistent YYYY-MM-DD format prevents timezone ambiguities.
• -No input sanitization: habit.name is directly inserted into DOM via textContent (safe from XSS but worth noting); no length validation on stored completions array.
• -Calendar rendering creates 14 new DOM nodes per habit on every render; no virtual scrolling or memoization, but acceptable at typical scale.
• -No destructuring or const declarations for frequently accessed DOM elements (habitList, emptyState) — minor stylistic miss.