/* public/style.css (PRETTIFIED & MOBILE FRIENDLY - Final Version) */

/* --- Variables & Global Setup --- */
:root {
    /* Color Palette */
    --color-primary: #34495e; /* Dark Blue/Gray */
    --color-secondary: #2ecc71; /* Green Success (Keypad Complete Highlight) */
    --color-accent: #e74c3c; /* Red Error/Active */
    --color-background: #ecf0f1; /* Light Gray Background */
    --color-border: #bdc3c7; /* Subtle Border */

    /* Sudoku Board Colors */
    --color-fixed-number: #34495e;
    --color-user-number: #2c3e50;
    --color-note: #667788;

    /* Highlighting */
    --color-highlight: #f1c40f33; /* Soft Yellow Highlight (20% opacity) */
    --color-selected: #3498db33; /* Soft Blue Selected (20% opacity) */
    --color-error-bg: #f7bbbb; /* Error Background */
    --color-same-number: #f1c40f33; /* YELLOW HIGHLIGHT for same numbers on board */

    /* Typography */
    --font-stack: 'Roboto', 'Arial', sans-serif;
    --box-shadow: 0 6px 15px rgba(0, 0, 0, 0.1);
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: var(--font-stack);
    background-color: var(--color-background);
    color: var(--color-user-number);
    display: flex;
    justify-content: center;
    /* Keeping flex-start to align content to the very top */
    align-items: flex-start; 
    /* Keeping min-height for development visibility, but removing padding */
    min-height: 100vh;
    padding: 0; /* REMOVED padding from body */
    user-select: none;
    line-height: 1.2;
}

/* --- Main Game Layout Container & Controls --- */

#game-container {
    width: 100%;
    max-width: 500px;
    background: #fff;
    border-radius: 12px;
    box-shadow: var(--box-shadow);
    /* ADJUSTED: Tighter padding */
    padding: 15px; 
    /* CRITICAL FIX: Removed margin-top to eliminate space above the board */
    margin-top: 0px; 
}

h1 { 
    text-align: center; 
    color: var(--color-primary); 
    margin-bottom: 20px; 
    font-size: 1.8rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

#control-panel { 
    display: flex; 
    justify-content: space-between; 
    align-items: center; 
    margin-bottom: 15px; 
    flex-wrap: wrap; 
    gap: 10px; 
}

#difficulty-selector-container { display: flex; align-items: center; gap: 5px; }

.control-select {
    padding: 6px 10px;
    border-radius: 6px;
    border: 1px solid var(--color-border);
    background-color: white;
    font-size: 0.9rem;
}

#timer { 
    font-size: 1.1rem; 
    font-weight: bold; 
    color: var(--color-primary); 
    display: flex;
    align-items: center;
    gap: 5px;
}

.control-btn {
    padding: 8px 15px;
    background-color: var(--color-primary);
    color: white;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: bold;
    transition: background-color 0.2s;
    display: flex;
    align-items: center;
    gap: 5px;
}
.control-btn:hover { background-color: #2c3e50; }


/* --- Message Bar --- */
#message-bar {
    text-align: center;
    margin-bottom: 20px;
    padding: 10px;
    border-radius: 6px;
    font-size: 0.9rem;
    min-height: 40px;
    transition: background-color 0.3s, color 0.3s;
}
.msg-default { background-color: #ecf0f1; color: var(--color-primary); }
.msg-success { background-color: var(--color-secondary); color: white; font-weight: bold; }
.msg-error { background-color: var(--color-accent); color: white; font-weight: bold; }


/* --- Sudoku Grid --- */

#sudoku-grid {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    grid-template-rows: repeat(9, 1fr);
    border: 4px solid var(--color-primary); /* Thicker outer border */
    margin: 0 auto;
    width: 100%;
    aspect-ratio: 1 / 1;
    overflow: hidden; /* Ensures borders are crisp */
}

.cell {
    border: 1px solid var(--color-border);
    cursor: pointer;
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: background-color 0.1s;
}

/* 3x3 Block Borders */
/* Vertical Borders */
.cell:nth-child(3n):not(:nth-child(9n)) { border-right-width: 3px; border-right-color: var(--color-primary); }
/* Horizontal Borders */
.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) { border-bottom-width: 3px; border-bottom-color: var(--color-primary); }
/* Fix for first row 3x3 border top edge */
.cell:nth-child(n+10):nth-child(-n+18),
.cell:nth-child(n+37):nth-child(-n+45) { border-top-width: 1px; }
.cell:nth-child(n+28):nth-child(-n+36),
.cell:nth-child(n+55):nth-child(-n+63) { border-top-width: 1px; }

/* --- Cell Content & Highlighting --- */

.cell .main-number {
    font-size: clamp(1.2rem, 5vw, 2.5rem); 
    font-weight: 700;
    z-index: 10;
    color: var(--color-user-number);
}

.cell.fixed .main-number { 
    color: var(--color-fixed-number);
    font-weight: 900;
}

.cell.error-highlight { 
    background-color: var(--color-error-bg) !important; 
    color: var(--color-accent);
}
.cell.error-highlight .main-number { color: var(--color-accent); }


/* Highlighting */
.cell.selected { background-color: var(--color-selected); }
.cell.highlight-same-num { background-color: var(--color-same-number); } 
.cell:hover:not(.selected) { background-color: var(--color-highlight); }


/* Pencil Marks (Notes) */
.cell .notes {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    grid-template-rows: repeat(3, 1fr);
    padding: 2px;
    box-sizing: border-box;
    pointer-events: none;
    opacity: 0.9;
}

.cell .notes span {
    font-family: var(--font-stack);
    font-size: clamp(0.5rem, 1.8vmin, 0.8em);
    color: var(--color-note);
    text-align: center;
    line-height: 1.1;
    display: block;
    font-weight: normal;
}

.cell.user-entered .notes { display: none !important; }


/* --- Keypad and Action Buttons --- */

#keypad-container {
    margin-top: 20px;
    display: flex;
    flex-direction: column;
    gap: 15px;
}

#action-buttons {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 10px;
}

#keypad {
    display: grid;
    grid-template-columns: repeat(9, 1fr);
    gap: 10px;
}

.action-btn {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 50px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    background-color: var(--color-background);
    color: var(--color-primary);
    font-size: 1.2rem;
    transition: background-color 0.2s, color 0.2s;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

.action-btn:hover { background-color: #e0e6e9; }

.action-btn.active {
    background-color: var(--color-accent); /* Active state color */
    color: white;
}

.action-btn.active:hover { background-color: #c0392b; }

.keypad-btn {
    height: 50px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.5rem;
    font-weight: bold;
    border: 2px solid var(--color-border);
    border-radius: 8px;
    cursor: pointer;
    background-color: white;
    color: var(--color-user-number);
    transition: background-color 0.1s, border-color 0.1s;
}

.keypad-btn:hover { background-color: #f5f5f5; }

/* Keypad selection highlight */
.keypad-btn.selected-key { 
    background-color: var(--color-selected); 
    border-color: var(--color-primary); 
}

/* Keypad Completion Highlight (Green) */
.keypad-btn.completed { 
    background-color: var(--color-secondary); 
    color: white;
    border-color: var(--color-secondary);
    opacity: 0.6;
}
.keypad-btn.completed:hover { opacity: 0.8; }

/* --- Mobile Responsiveness --- */
@media (max-width: 600px) {
    #game-container {
        padding: 10px;
        /* CRITICAL FIX: Ensure margin-top is zero on mobile */
        margin-top: 0px; 
        box-shadow: none;
        border-radius: 0;
    }

    #control-panel {
        flex-direction: row;
        gap: 8px;
        justify-content: space-around;
    }
    
    #difficulty-selector-container { order: 1; }
    #timer { order: 2; }
    #new-game-btn { order: 3; flex-grow: 1; padding: 10px 10px; }

    #action-buttons {
        grid-template-columns: repeat(5, 1fr);
        gap: 5px;
    }

    .action-btn {
        height: 45px;
        font-size: 1.1rem;
    }

    .keypad-btn {
        height: 45px;
        font-size: 1.3rem;
    }
}