✏️ Desk Check #1: Simple Sequence

Let us desk check this simple algorithm together, one step at a time.

🐍 Fortnite Shield Calculator

health = 100
shield = 50
damage = 80

if shield > 0:
    shield = shield - damage
    if shield < 0:
        health = health + shield
        shield = 0

print("Health:", health)
print("Shield:", shield)

📋 Step-by-Step Trace Table

Step 1 — Line 1: `health = 100`

The variable health is created and set to 100. No other variables exist yet.

Step	Line	health	shield	damage	Output
1	1	100	—	—	—

Step 2 — Line 2: `shield = 50`

The variable shield is created and set to 50.

Step	Line	health	shield	damage	Output
1	1	100	—	—	—
2	2	100	50	—	—

Step 3 — Line 3: `damage = 80`

The variable damage is created and set to 80.

Step	Line	health	shield	damage	Output
1	1	100	—	—	—
2	2	100	50	—	—
3	3	100	50	80	—

Step 4 — Line 5: `if shield > 0:` → 50 > 0 is TRUE

Shield is 50, which IS greater than 0. So we enter the if block.

Step 5 — Line 6: `shield = shield - damage` → 50 - 80 = -30

Shield becomes -30. That is negative! The damage was more than the shield could absorb.

Step	Line	health	shield	damage	Output
3	3	100	50	80	—
5	6	100	-30	80	—

Step 6 — Line 7: `if shield < 0:` → -30 < 0 is TRUE

Shield IS negative, so the overflow damage carries to health.

Step 7 — Line 8: `health = health + shield` → 100 + (-30) = 70

Adding a negative number is the same as subtracting. The 30 overflow damage reduces health from 100 to 70.

Step 8 — Line 9: `shield = 0`

Shield is reset to 0 (it cannot be negative in a game).

Steps 9–10 — Lines 11–12: Print statements

Step	Line	health	shield	damage	Output
1	1	100	—	—	—
2	2	100	50	—	—
3	3	100	50	80	—
5	6	100	-30	80	—
7	8	70	-30	80	—
8	9	70	0	80	—
9	11	70	0	80	Health: 70
10	12	70	0	80	Shield: 0

✅ Desk Check Complete!

Run the code above and confirm: Health is 70, Shield is 0. Our desk check matches the actual output. The algorithm correctly handles overflow damage from shield to health.