Platformer

Build a platformer from a blank project. Day 1 is gravity and jumping, Day 2 is platforms and collision, Day 3 adds an objective and score. Boolean operators do the heavy lifting, so read Boolean Operators first if and, or, and not are new.

Schedule

Project Day 1: Gravity

Ground and Basic Gravity

1. Create a sprite named ground. Draw a filled rectangle across the bottom of the costume, wide enough to span the stage.
2. On the player sprite, make it fall whenever it is not touching the ground:

when green flag clicked
forever
  if <not <touching [ground v]?>> then
    change y by (-5)
  end
end

3. Add a jump that only works from the ground:

when [space v] key pressed
if <touching [ground v]?> then
  change y by (10)
end

4. Add left and right movement on your own. Either movement pattern works.

Gravity With Velocity

Fixed-speed gravity falls at the same rate forever. Real objects accelerate. Create a variable called velocity (for all sprites) and switch to the Gravity and Velocity pattern:

when green flag clicked
set [velocity v] to (0)
forever
  if <not <touching [ground v]?>> then
    change [velocity v] by (-1)
  else
    set [velocity v] to (0)
  end
  change y by (velocity)
end

Then change the jump to set velocity instead of moving the sprite directly — the Jumping pattern:

when [space v] key pressed
if <touching [ground v]?> then
  set [velocity v] to (10)
end

Experiment. A stronger jump is set [velocity v] to (20); stronger gravity is change [velocity v] by (-2). Find values that feel good.

Practice tracing this code frame by frame: Gravity and Velocity: Quiz Examples.

Project Day 2: Platforms and Collision

Full steps on the Platforms and Collision page. In short:

1. Redesign the player. Small (30–40 px wide), simple shapes, solid fill, facing right. Scratch the cat is too big and has transparent gaps that confuse touching.
2. Platforms. One sprite named platform with several filled rectangles on one costume. One touching [platform v]? block covers all of them.
3. Land on platforms with or, move before you check, and bounce gently on landing — Landing on Platforms.
4. Jump from platforms by adding or touching platform to the jump’s condition.
5. Wall collision with the step-up test — Wall Collision. Switch movement to the A and D keys so one hand handles movement and the other handles space.

Known bug: jumping into the underside of a platform can stick the player to it. Space platforms so the player lands on top instead of hitting from below.

Project Day 3: Objective and Score

Use the starter project only if your own code is not working.

1. Create an objective sprite — a coin, star, gem, or key, about 20–30 pixels so it fits on a platform.
2. Place it on a platform the player has to work to reach.
3. Make a score variable (for all sprites) and set it to 0 when the green flag is clicked.
4. Detect collection on the objective sprite: when touching the player, hide, and change [score v] by (1).
5. Reset the player to the starting position after a collection, for example go to x: (-200) y: (-100), so the player has to cross the platforms again.
6. Respawn the objective after a short wait, in the same or a new position, so the loop continues.

when green flag clicked
set [score v] to (0)
show
forever
  if <touching [Player v]?> then
    change [score v] by (1)
    hide
    wait (2) seconds
    go to [random position v]
    show
  end
end

Share with a partner and play each other’s games. What do you like? What would you change?

Resources

• Platforms and Collision — the full Day 2 lesson with every code block.
• Platformer Build-Along — a start-to-finish script, from a blank project through wall collision, with vocabulary.
• Scratch Code Patterns — gravity, jumping, landing, and wall collision in one place.

Checkpoints

Day 1

• The player falls and stops on the ground.
• The player jumps with space, only from the ground.
• Gravity uses a velocity variable and the fall speeds up.

Day 2

• I drew a new, smaller player with simple shapes and a solid fill.
• The player lands on platforms and jumps from them.
• The player stops when walking into the side of a platform.
• There are at least three platforms at different heights.

Day 3

• An objective sits on a platform.
• Touching it adds 1 to score, hides it, and resets the player.
• The objective reappears so it can be collected again.

Teacher Notes

• Day 1 works best as a review warmup (rebuild basic gravity) followed by the velocity upgrade as the work session.
• Day 2 is the densest day. Students who get stuck on wall collision can skip it and still have a playable game.
• The head-bump bug is real and students will find it. Acknowledging it up front beats pretending it does not exist.
• A Code.org nested-loops lesson makes a good warmup for Day 3 while you check Day 2 projects.