Envahi Remastered

Envahi ("Invaded" or "Overrun") is a Commodore VIC-20 arcade shooter for a VIC-20 with 8K memory expansion. Fly your helicopter over the city, shoot straight up, and keep the invaders away from the city below, and from the dam holding back the city reservoir.

This remastered edition is the original Virgin Games release taken apart, fully commented, and rewritten from its BASIC-and-machine-code original into pure machine code. The game has had several enhancements made after optimising it to make extra space.

How it plays:

Aliens fly in from the right to attack the dam. Three hits on the same part and it breaks, causing the reservoir to pour through and flood the city. We hope you can swim.

The mothership crosses the sky dropping aliens onto the city. Any that land will cause an Invasion. If one hits your helicopter then it will be destroyed. You can now however destroy the mothership with five hits for an extra 500 points.

A Zoomer zig-zags down the screen, an acid cloud rains hell down on you, and an abductor may just come down and carry your ship away, leaving the city to fall.

Be careful not to fly into any building, or the dam itself, else you're toast.

Every wave the aliens get faster and more numerous, and the sky moves on from morning, afternoon, evening to nightfall.

You get 3 lives, with an extra life every 2000 points. You also now get one smart bomb for each life.

What's new in this remaster:

All machine code: the original ran its background game loop from 43 lines of BASIC; but now it's one fast, smooth program, playing at the original's pace.

Title screen with credits, a high score table (top 4, with your initials), skill selection and a demo mode that plays itself as an attract mode.

A new title tune in two voices (the original tune plays while you enter your initials).

Day and night cycle. The sky changes each wave, with twinkling stars at night time.

The mothership can be destroyed, the cloud leaves after 15 seconds, and "WAVE n" announces each new wave.

Smart bomb (RETURN), pause (P), music (M) and sound (S) switches.

New effects: firing, the dam cracking, an extra life jingle, explosion debris, a red flash when you lose a life, and a waterfall through the broken dam.

Three skill levels: EASY, NORMAL (the original) and HARD.

PAL and NTSC: the game checks which machine it's on and runs at the same speed.

Fixes for the original's bugs — among them the helicopter freezing when the abductor took a building, aliens being shot in the wrong lane, and objects falling off the bottom of the screen into the program memory. For some strange reason the program code allowed this and kept those 27 bytes clear of program code. Maybe a bug that they never had time to fix?

Controls:

Fly - Joystick, or Z left · X right · ; up · / down.

Fire - Fire button or SPACE.

Smart bomb - RETURN (one per life).

Pause - P.

Music / Sound - M and S.

Skill level selection - Joystick left / right on the title screen.

Start - Fire on the title screen.

Envahi was created by Jeremy walker and published by Virgin Games.

This remaster was created by Tony Brice with the assistance of Claude.