Professor Zappy: Circuit Defense

How to play

The goal

Electrons are racing along a wire toward Professor Zappy. He starts every level with just 1 HP, and each electron that reaches him costs HP (green ones cost 2), so buy him some health before you start. Survive every wave to clear the level. There are 50 levels. Level 1 is a guided tutorial that walks you through everything step by step (there’s a Skip tutorial button if you already know how). New things arrive gradually: resistors and blue electrons on level 2, red electrons and capacitors on level 4, green electrons and Zener diodes on level 7 and the fuse on level 11. Every 10th level is a boss level with an extra wave, and the maps get trickier as you go.

1. Draw the path, like a real breadboard

• One lead per hole. Every hole holds just one wire end or one part leg, so two jumpers can never share a hole.
• Burnt holes (red X): nothing fits in them, and wires and parts can’t cross them. Later levels use lines of X’s as walls, mazes and chokepoints, so look for the gap.
• Inside the board, holes are joined by hidden metal strips. Holes a–e in the same numbered column are connected, f–j likewise, and each rail (+ or −) is connected along its whole length. Current flows along a strip on its own.
• The 9V battery’s lead makes its strip glow. On the first levels that’s the red + rail; later the battery and Professor Zappy move to other rows. Drag from any glowing hole to another hole in the same row or column to lay a jumper wire (up to 6 holes long), or tap the start hole and then the end hole.
• When a jumper lands, its whole strip lights up. Start the next jumper from another free hole in that strip and watch the current travel along the strip to it. Each strip can only be used once.
• Keep hopping strip to strip until a jumper lands in Zappy’s strip (outlined in purple next to him). A current pulse runs down the wire: circuit complete! Only then can you press Start.
• Wire costs money: $1 per hole of jumper, paid as you lay it (the label next to your finger shows the length and price while you drag). Undo and Clear give the money back before you press Start. The Wire meter shows how much wire you’ve used out of the level’s maximum and what it cost. Electrons travel at the same speed through strips and jumpers, so a longer, winding path gives your parts more time to work. That’s the puzzle.
• Red flash + buzz = not allowed: a hole that’s already taken (“One lead per hole”), diagonal jumpers, burnt holes (red X) or a jumper that would cross one, a strip you already used, a − rail (that would short the battery), running out of wire, or not having enough money for it.
• ↶ Undo removes the last jumper, ✖ Clear starts over.

2. Place parts

Every part has two legs, and each leg needs its own free hole: not one with a wire end or another leg in it, and not one a jumper is lying across. Both legs can’t sit in the same connected strip (that would short the part out), and the part has to sit right next to the wire or on a strip the current runs through. Parts are bought with your money: the price is on each part in the tray, and parts you can’t afford are greyed out. Drag a part from the tray onto the board, or tap the part and then a hole. While you aim, a preview shows both legs: green fits, red doesn’t. Press R (or the ↻ R button in the tray on a phone or tablet) to rotate the part between horizontal and vertical. While you aim, its range shows as a circle around the part’s middle (green = fits, red = doesn’t). Tap a placed part to see its range and stats in a small panel, upgrade it, or press Return to sell it back for the full price (before you press Start; upgrade money comes back too). You can also buy parts between waves and during a wave. Each level also limits how many of each part you can use; the message tells you when you hit the limit.

• Resistor ($10): anything in its range is slowed down and loses energy every second. Resistors are your main defense. Put them where the wire bends so they cover more of it.
• Capacitor ($18): charges up (watch the blue ring), then zaps every electron nearby at once and stuns them for a moment. Then it recharges.
• Zener diode ($22): blocks the wire at its spot (red bar), holding electrons back and draining them, then breaks down (yellow) and lets them through, then recovers. Great in front of a capacitor.
• Fuse ($30, from level 11): single use. During a wave, tap it to blow it and wipe out that whole wave. Save it for the scariest one.

3. Money $, health and upgrades

Everything is bought with money ($), shown at the top: wire, parts, upgrades and Zappy’s health. Each level gives you a budget ($34 in the tutorial and $65 on level 2, rising $5 a level to $300 on level 49, with more on boss levels: $365 on level 50), plus half of the money you had left when you cleared the level before. Saving pays off a little, but it’s better to spend wisely. Retry puts your money back to what you started the level with.

• Earn more by destroying electrons (blue $1, red $2, green $3), clearing a wave ($3) and clearing a level ($10 plus $2 for every HP Zappy has left). You can spend it straight away, even in the middle of a wave.
• Health: press +♥ next to Zappy’s health bar to buy 1 HP. The first extra heart costs $4, and each one after that costs $1 more. Each level has a maximum: 10, then 12 from level 20, and 2 more on boss levels. You can buy health before Start and during waves.
• Upgrades: tap a part and spend money on three tracks, three levels each ($8, then $14, then $22, and each upgrade you buy makes the next one on that part $3 dearer). Coloured pips on the part show its upgrades.

• Range (blue pips): reaches further.
• Power (red pips): more damage.
• Special (yellow pips): resistor slow lingers after electrons leave its range; capacitor recharges faster and stuns longer; Zener holds the wire longer; fuse re-arms once (and later refunds $12).

Tip: a long, winding wire, a few well-placed parts and two or three hearts usually beats spending everything on one thing.

4. Start the waves

Press ▶ Start. Waves come one after another. Blue electrons are the normal kind, red ones are fast but fragile, and green ones are slow, tough and hit harder. ⏩ speeds the game up, and the speaker button mutes it.

You can see every part firing: orange beams are resistors draining electrons, a blue shock ring with arcs is a capacitor zap, a red barrier on the wire is a Zener holding electrons back, and the whole wire flashes when a fuse blows. Small numbers show the damage.

Tip: electrons that sit still inside a resistor’s range lose energy the fastest. A Zener or a capacitor stun next to your resistors makes them much stronger.

5. 50 levels and saved progress

Levels unlock one at a time. Press Levels ▦ to open the level grid: cleared levels show stars (3 = Zappy never got hit, 2 = hit once or twice, 1 = cleared), and boss levels are marked. Your progress is saved only in this browser, and next time the game continues where you left off. Playing on from one level to the next carries half your leftover money; a level picked from the grid starts with its normal budget.

Your level progress and sound on/off choice are saved only in your own browser (localStorage). Nothing is sent anywhere.

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