Build an HTML5 platformer in a single file (HTML/CSS/JS).
Theme: neon skyline at sunset with soft gradients and glowing UI.
Core loop: run -> jump -> collect combo coins -> avoid enemies.
Mechanics: double-jump, moving platforms, checkpoints every ~30 seconds.
Controls: Arrow keys or A/D to move, Space to jump, R to restart.
UI: score, lives, combo meter, and a short tutorial panel.
Win condition: reach a finish flag OR survive 60 seconds.