Stack city online appears simple but can be annoying fast. I tried it, and controlling the physics and timing makes it tricky for me to stop trying.
Match and place blocks carefully, and try to build higher with fast precision.
About controls are not explicitly stated, so focus on stacking, dropping, and lining up blocks accurately.
Watch how the blocks fall and adjust your timing, small changes can improve your stacking accuracy.
Q: What are the controls? A: Not stated.
Q: What is the main objective? A: Stack blocks to go higher.
Q: Are there modes or hints? A: Not stated.
Q: What is the main mechanic? A: Drop and line up blocks.