body {
    font-family: system-ui, sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 2rem;
    background: white;
}

#board {
    display: grid;
    grid-template-columns: repeat(9, 40px);
    grid-template-rows: repeat(9, 40px);
    border: 2px solid #333;
    margin-bottom: 1rem;
}

#logo{
    max-width: 200px;
    margin-bottom: 1rem;
}

#board input {
    width: 100%;
    height: 100%;
    border: 1px solid #ccc;
    text-align: center;
    font-size: 1.2rem;
    background: white;
    box-sizing: border-box;
    transition: background-color 0.3s ease;
    caret-color: transparent;
}

#board input.valid {
    background-color: #90ee90;
}

#board input.invalid {
    background-color: #ffb3b3;
}

#board input.fixed {
    background: #e0e0e0;
    font-weight: bold;
}

#board input.player {
    background: lightblue;
    font-weight: bold;
}

/* thicker borders to mark 3x3 boxes */
#board input[data-col="2"],
#board input[data-col="5"] {
    border-right: 2px solid #333;
}

#board input[data-row="2"],
#board input[data-row="5"] {
    border-bottom: 2px solid #333;
}

#controls {
    display: flex;
    gap: 0.5rem;
    align-items: flex-start;
}
.control-slot {
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: center;
    min-width: 100px;  /* keeps slots stable */
}

#new-puzzle-container {
    display: flex;
    flex-direction: column;
    align-items: center;
}

#difficulty-selector {
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%);
    margin-top: 0.5rem;
    display: flex;
    gap: 0.3rem;
}

#difficulty-selector.hidden {
    display: none;
}

.difficulty-btn {
    padding: 0.25rem 0.6rem;
    font-size: 0.8rem;
}


button {
    padding: 0.5rem 1.5rem;
    font-size: 1rem;
    cursor: pointer;
    border: none;
    border-radius: 20px;
    background-color: #4a90d9;
    color: white;
    transition: background-color 0.2s ease;
}

button:hover {
    background-color: #357abd;
}

#difficulty-selector {
    margin-top: 10px;
}

#difficulty-selector.hidden {
    display: none;
}

.difficulty-btn {
    background-color: darkred;
    color: white;
    margin: 0 5px;
}

#instructions {
    height: 1.5rem;
    color: black;
    font-size: 0.9rem;
}
#status {
    height: 1.5rem;
    color: darkblue;
    font-size: 0.9rem;
}