Smooth experience, plays like an abstracted infinite runner although I feel I'm fare less in danger due to being a square. The primary obstacle/enemy is often just speed when surviving far into the game. Generally a good average game beat the high score. Suggestion below will make the game more Unique as oppose to just "good".
Improvement On Graphics:
1) TARGET: Appearance of play, level hazards, collectibles and interactive elements rarely change. Does every single ground hazard have to be a triangle? You can change the sprite every score ranks/minutes, to provide variety. After 15 minutes, I'm tired of triangles and squares. Changing the art at critical moments can be a subtle reward for the player.
1) DESIGN SOLUTION : Please see a game called ICY TOWER, it's a high-score survival game just like this, where they change the art while keeping the mechanics relatively the same. You can brag to friends that you survived to the Ice Zone, because reaching that Art Style means you lasted past 5000 points / 20 minutes-----it's a satisfying reward that the world changes.
2) TARGET: The interactive items & player should also vary more than this. If I've survived for 30 minutes, I'd be expected to pick up Gold glowing keys, as an example. When I first see the key, I know it's important, however when as an Important Item, I never feel like "I WANT that shiny KEY!". Instead it's just a passive pickup along a level, that never change form or shape. This include the player as a square. The boundary of the player may not be able to change, however other elements of your appearance can change as you advance, to make me feel more special for surviving.
2) DESIGN SOLUTIONS:
a) THE KEY/ITEMS: Make me want it! Give it a glow, change it's color as you go along, give it sparks, give it an effects trail sometimes, make it a double-golden key! Keys come in all manner of shapes in real life too!
b) THE PLAYER: Make me change over time. Give me a new effects trail, change my square color, let my square have a face, give my square an inner glow and outer glow. Make me want to survive to get the electric abstract particles behind me and a neon two-color square. The player is the most interactive and long-lasting thing in the entire game, shouldn't I change & evolve even subtlety over time as I progress??
c) INTERACTIVE: Apply the above Progressive Variance concept to other art where possible. For example with the ghost-art: it could be a two-headed ghost sometimes; a small ghost inside a big ghost; it can be a ghost with fangs where is X face is. I'm unsure why there is a ghost in a world of abstract non-living shapes, but since real-life people are familiar with the concept of a ghost in games, stretch their imagination.