Speed Spell

Speed Spell starts by splitting the 120-card letter deck among the players. Each player draws a hand of 5 cards from their deck, and one player starts by laying down one or more letters together on the table that can form part of a word.

Then without taking turns, players place cards from their hand on either end of any letter group on the table. A player can start a new group with 1 or more cards if and only if all other groups have at least 3 letters. After playing cards, players fill their hand back out to 5 cards from their deck.

Once a player adds to a group to spell a valid word of 4+ letters, they say the word aloud and claim all its cards to place in their winnings pile. But a newly claimed word can be stolen by another player if they lay down a single card could be added to an end of the word to make another word. (E.g. STUN can be stolen by adding a T to make STUNT, and stolen again by adding an S to make STUNTS.)

The game ends once one player has run out of cards in both their deck and hand. Each player's score is 1 point per card in their winnings pile, minus 1 point per card still in their deck and hand. The highest score wins.

There is also a turn-based version, with these differences:

 Hands have 7 cards, not 5. 
 Words must have 5+ letters, and to start a new letter group, all other groups must have 4+ letters. 
 A player may also move a letter from the end of one group to an end of another group, as long as at most one group has 3- letters. 
 During their turn a player takes as many actions as they wish, after which they fill their hand back up to 7. 

Words claimed during a player's turn may still be stolen by other players.