One- or Two-Button Game Design Guide
Building accessible games and apps for Ben and families like ours. This guide provides comprehensive principles, input models, and best practices for creating experiences that work with just two keys: Spacebar and Return.
Quick Navigation
Core Principles
- Entire app and every game must be fully usable with only two keys: Spacebar and Return, plus optional mouse or touch for caregivers or users who have those access options.
- No reflex or time-limit mechanics. Use puzzles, logic, sequencing, matching, turn-based choices, and exploration.
- All actions should be available through scanning and selection. Nothing should require precise timing.
Input Model
Spacebar Controls
- Short press (release): Move highlight forward in the current scan list. Activates on release so accidental holds don't trigger selection.
- Hold 3+ seconds: Enable auto-scan forward until release. Release stops auto-scan.
Return Controls
- Short press (release): Select the currently highlighted item.
- Hold 1.5+ seconds: Open context or pause menus, or exit sub-modes. Use this for options, help, or a safe back button.
Mouse or Touch (Optional)
- For caregiver support or for individuals who have mouse, touch, or eye-tracking access.
- Click to select, click and hold to open context menus when appropriate.
- Never require dragging.
Scanning Behavior
- Scanning starts only after the first Spacebar press in a scene or game.
- Row scanning: Spacebar cycles rows, Return enters a row. Within a row, Spacebar cycles buttons, Return selects.
- Deadzone at wrap: Before a list wraps to the top, insert one scan step with no highlight to let the screen "rest."
- Predictable loop order: Top to bottom, left to right. Never reorder during a session.
- Focus memory: When returning from a submenu, restore highlight to the last focused item.
Visibility and Audio
Visual Design
- High-contrast UI by default, large hit targets, generous spacing
- Global font scaling controls with presets: 100, 125, 150, 175, 200 percent
- Color profiles: High Contrast, Light, Dark, and Ben Default (brand colors)
- Optional outline thickness control for the highlight ring
Text-to-Speech
- TTS for all labels, menu names, states, and outcomes
- Speak on focus and on selection
- Provide a TTS rate control and a volume control
- TTS should never block input
Layout and Components
- Consistent header: Title, Help, Settings, Exit to Main Menu
- Footer: Current mode, current scan target name, and a simple legend:
Space = next,Return = select,Return hold = menu - All dialogs and menus scannable using the same pattern as gameplay
- Large buttons, minimum 64px height on tablet
- Avoid small tap targets
- Never require keyboard keys other than Spacebar and Return
Game Mechanics That Work Well
Golden rule: Turn-based puzzles, no timers, no sudden fail states.
Recommended Mechanics
- Matching and memory games
- Pattern sequencing and Simon-style repetition (without timing)
- Sorting and categorization
- Grid navigation with obstacles and keys
- Jigsaw or tile assembly with rotate and place
- Spot the difference
- Non-timed maze traversal with step-by-step moves
- Logic puzzles with yes or no choices
- Story choices with inventory gates
- Picture building or coloring by areas, stepwise fills only
- Word building with predictive suggestions
- Simple math or shapes, one step at a time
Mechanics to Avoid
Never use: Timers, falling objects, health decay, platforming, reaction tests, QTEs, hold-to-aim precision, multi-axis analog control.
Feedback and State
- On focus change: Speak the item name and show a strong highlight
- On selection: Speak confirmation and show a brief glow or scale pulse
- On error or locked action: Speak a short helpful line (e.g., "Need the key for this door")
- Always provide Undo or Back in the context menu reached by Return hold
Menus and Pause
- Return hold opens Pause or Context anywhere. Include Resume, Restart, Help, Settings, Exit
- Hold Return should also back out of sub-rows to row-select mode
Settings to Include
- TTS on/off, rate, volume
- Highlight style: color, thickness, pulse on/off
- Font size presets
- Color profile and contrast
- Scan speed for auto-scan
- Audio cues on/off
- Reduce motion on/off
Data and Persistence
- Auto-save progress on each selection that changes state
- Resume puts the player back in the exact frame with the previous highlight restored
- Keep a per-game Settings profile, and a global default
QA Checklist Before You Ship
- ✓ Can every action be performed with only Spacebar and Return?
- ✓ Can the same action be performed with mouse or touch when needed?
- ✓ Does scanning begin only after the first Spacebar press?
- ✓ Do Spacebar short, Spacebar hold, Return short, Return hold all behave as specified?
- ✓ Is there a deadzone before wrap?
- ✓ Are fonts readable at 100% on a tablet and adjustable to 200%?
- ✓ Does TTS read focus, selection, errors, and outcomes?
- ✓ Can the player open Pause with Return hold on every screen?
- ✓ Are there no timers or reflex steps anywhere?
- ✓ Does the game auto-save and resume correctly?
Example: P3GL (Peggle-style Game) Input Setup
Here's an example of how a two-button setup can power a complete skill-based puzzle game without requiring reaction timing:
P3GL Input Model
- Spacebar (short press): Start the aim oscillation left to right
- Spacebar (long hold): Reverses the aim direction after each click, allowing fine-tuned aiming with one button
- Spacebar (release): Stops movement and locks in aim
- Return (short press): Fires the shot or launches the ball
- Return (long hold): Opens the pause or options menu (Resume, Restart, Exit)
This allows Ben to aim, adjust, and fire entirely with one button for control and one button for confirmation, keeping it accessible, predictable, and satisfying without any time-based input or precision demand.
Get in Touch
Have questions or want to contribute? Reach out to us.