What students build
- A controllable catcher
- Repeated falling snowballs
- Random starting positions
- Collision and missed-object rules
- Score and loss state
- Reliable restart
Guided Project
Guided ProjectAttack of the Angry Snowballs
Move the catcher, survive the changing attack patterns, and keep the town's emergency cocoa out of the snow.
Project brief
What students learn
- Choosing a loop
- Random x positions
- Changing y over time
- Collision checks
- Variables and difficulty
- Testing repeated events
What students need
- Browser
- Scratch editor
- Keyboard
- Student-drawn or ordinary built-in assets
The project works with built-in or student-drawn artwork. Saving and sharing depend on the classroom setup.
Suggested build order
- 01
Create the catcher
Task: Put a player-controlled catcher near the bottom of the stage.
- Checkpoint
- The left and right controls work without leaving the stage.
- Likely mistake
- Changing y instead of x.
- 02
Make one snowball fall
Task: Start one snowball above the stage and change its y position inside a loop.
- Checkpoint
- The snowball crosses the stage from top to bottom.
- Likely mistake
- Moving once instead of inside a loop.
- 03
Move the next attack
Task: Choose a new x position before each fall.
- Checkpoint
- Several falls begin in different places.
- Likely mistake
- Choosing a new x during every movement step.
- 04
Separate catches from misses
Task: Write one rule for touching the catcher and another for passing the bottom edge.
- Checkpoint
- Each fall has one outcome and changes the score once.
- Likely mistake
- Scoring repeatedly while the sprites still touch.
- 05
Build the waves
Task: Repeat the fall-and-reset cycle, then shorten the delay after a chosen score.
- Checkpoint
- The speed changes at the score you chose.
- Likely mistake
- Making the objects too fast to test.
- 06
Reset the storm
Task: Restore the score, speed, positions, and game state.
- Checkpoint
- Three restarts produce the same first wave.
- Likely mistake
- Resetting the score but keeping the faster speed.
Test questions
- Can every snowball be caught?
- Does a miss count once?
- Can a snowball appear outside the playable area?
- Does speed change at the intended score?
- Does restart restore the first-wave timing?
Common mistakes
- Random x changes during the fall.
- The miss line is outside the stage.
- Catch and miss happen in the same frame.
- A forever loop prevents the loss screen.
Extension ideas
- Add a rare giant snowball.
- Create two wave patterns.
- Add a temporary shield.
- Make wind change horizontal movement.
Challenge levels
Builder
Add a survival timer.
Inventor
Create a readable wave system with changing delays.
Boss Level
Design three attack patterns and select them from game state.
What to demonstrate
- Working catcher movement
- A repeated attack
- Catch and miss outcomes
- A visible score
- One difficulty change
- One repaired loop bug