Landing Page Pattern: Dark Modal Checkout. Keywords: modal checkout, in-app upgrade, dark modal, plan upgrade, subscription checkout, in-app purchase. Section Order: 1. Modal overlay on dark backdrop, 2. Plan comparison or selected plan card, 3. Payment form (card input), 4. Billing toggle (monthly/annual), 5. Subscribe/upgrade CTA. Primary CTA Placement: Subscribe button bottom of modal + Annual toggle top. Color Strategy: Dark modal bg: #1A1A1A or #0F0F0F. Card input: Dark input #2A2A2A with light border #404040. CTA: Brand accent (purple/blue/green). Annual savings badge: Green or accent. Text: White #F5F5F5.. Recommended Effects: Modal slide-up, billing toggle switch, plan card glow on featured tier, payment input focus glow. Conversion Optimization: Common for SaaS in-app upgrades. Show annual savings prominently. Highlight current plan vs upgrade. Stripe Elements for card input. Close button + click-outside-to-dismiss. Mobile: full-screen sheet instead of modal..