Tetris (PC, Spectrum HoloByte)

One of the Tetris games Spectrum HoloByte developed before losing their legal battle with Nintendo.

Timing
Timing is based on video frames, which are approximately 1/70 of a second.
 * Gravity makes a piece fall by one row every 20 - (level * 2) frames.
 * Lock delay is 16 frames.
 * Line clear delay is 20 frames.
 * ARE is 2 frames.

Scoring
Placing a piece awards score according to the following formula: The bottom row is number 1. If the piece was dropped manually, the position before dropping is used, so for a high score the player should drop as soon as possible.
 * points = 4 + (2 * level) + row number of top of piece

If piece preview is enabled at the time a piece is placed, a 25% penalty is assessed: (both divisions are rounded down)
 * points with preview on = floor(points / 2) + floor(points / 4)

No additional points are awarded for line clears.