Building Games in 2D

A working reference for the systems that make a 2D game feel responsive and look coherent.

Sprites and Animation

Art that is loaded and drawn efficiently keeps frame times low and motion legible.

How to organize sprite data:

• Texture atlas — pack many images into one sheet so the GPU issues fewer draw calls. A character's idle, walk, and jump frames all live on a single sheet rather than as 30 separate files.
• Frame sequence — an ordered list of regions on the atlas, cycled to produce motion.
• Pivot point — the anchor used for rotation and scaling. Put a sword's pivot at the handle, not the center, so it swings correctly.
• Z-order — the integer that decides who draws on top. The player's z sits above the floor tiles but below the HUD.

Making motion feel alive:

• Animate somewhere between 8 and 24 frames per second depending on the style — chunky retro sprites read fine at the low end, fluid action wants the high end.
• Compress and elongate shapes (squash & stretch) on impacts and jumps to sell weight.
• Lead into a big action with a brief wind-up (anticipation) — a crouch before a leap.
• Let motion settle afterward (follow-through) instead of snapping to a stop.

Tilemaps

Grid-based levels are fast to author and cheap to render.

A typical layer stack, back to front:

1. Backdrop — distant scenery you can never touch.
2. Ground — the solid tiles the player stands on.
3. Objects — chests, switches, pickups the player interacts with.
4. Overlay — foreground elements that scroll at a different rate for parallax depth.

Collision and Physics

Key choices when wiring up physics:

• Decide early between pixel-perfect movement and a physics-driven body — blending the two invites jitter and tunneling.
• Step the simulation on a fixed timestep so behavior stays identical regardless of frame rate.
• Use collision layers to control what tests against what — bullets check enemies, not other bullets.

Cameras

Screen shake, used with restraint:

• Keep bursts brief — roughly 50 to 200 ms.
• Ramp the intensity down over the burst rather than cutting it dead.
• Reserve it for moments that matter; constant shake just fatigues the eye.

Genre Movement

Platformers live or die on jump feel:

• Coyote time — accept a jump input for a few frames after the player walks off a ledge.
• Jump buffering — remember a jump pressed slightly before landing and fire it on touchdown.
• Variable height — cut the upward velocity when the button releases so taps hop and holds soar.

Top-down games turn on movement granularity:

• Pick 8-direction snapping or free analog motion to match the feel you want.
• Choose between manual aiming and auto-targeting based on how twitchy the combat should be.
• Decide whether the sprite rotates to face its heading or stays upright.

Mistakes to Avoid

Bottom line: in 2D there is nowhere to hide — make every pixel say something.