/* ============================================
   CALCULATOR - CSS STYLES
   ============================================ */

/* CSS Variables */
:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --secondary-color: #8b5cf6;
    --success-color: #22c55e;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;

    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;

    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;

    --border-color: #334155;
    --shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5);

    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-full: 50%;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    background-image:
        radial-gradient(at 0% 0%, rgba(99, 102, 241, 0.15) 0px, transparent 50%),
        radial-gradient(at 100% 100%, rgba(139, 92, 246, 0.15) 0px, transparent 50%);
}

/* Container */
.container {
    width: 100%;
    max-width: 400px;
}

/* Header */
.header {
    text-align: center;
    margin-bottom: 24px;
}

.header h1 {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
}

.header h1 i {
    color: var(--primary-color);
}

.header p {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-top: 4px;
}

/* Calculator */
.calculator {
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 20px;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-color);
}

/* Mode Toggle */
.mode-toggle {
    display: flex;
    background: var(--bg-tertiary);
    border-radius: var(--radius-md);
    padding: 4px;
    margin-bottom: 16px;
}

.mode-btn {
    flex: 1;
    padding: 10px;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: all 0.3s ease;
}

.mode-btn.active {
    background: var(--primary-color);
    color: var(--text-primary);
}

.mode-btn:hover:not(.active) {
    color: var(--text-primary);
}

/* Display */
.display {
    background: var(--bg-primary);
    border-radius: var(--radius-md);
    padding: 20px;
    margin-bottom: 16px;
    min-height: 100px;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    align-items: flex-end;
    overflow: hidden;
    border: 1px solid var(--border-color);
}

.previous-operand {
    color: var(--text-muted);
    font-size: 1rem;
    min-height: 24px;
    word-wrap: break-word;
    word-break: break-all;
}

.current-operand {
    color: var(--text-primary);
    font-size: 2.5rem;
    font-weight: 600;
    word-wrap: break-word;
    word-break: break-all;
    max-width: 100%;
    transition: font-size 0.2s ease;
}

.current-operand.small {
    font-size: 1.8rem;
}

.current-operand.smaller {
    font-size: 1.4rem;
}

/* Scientific Buttons */
.scientific-buttons {
    display: none;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    margin-bottom: 16px;
}

.scientific-buttons.active {
    display: grid;
}

/* Buttons Grid */
.buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}

/* Button Styles */
.btn {
    padding: 18px;
    font-size: 1.25rem;
    font-weight: 500;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all 0.15s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

.btn:active {
    transform: scale(0.95);
}

/* Number Buttons */
.btn-number {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.btn-number:hover {
    background: #475569;
}

/* Operator Buttons */
.btn-operator {
    background: var(--primary-color);
    color: var(--text-primary);
}

.btn-operator:hover {
    background: var(--primary-dark);
}

/* Clear Buttons */
.btn-clear {
    background: var(--danger-color);
    color: var(--text-primary);
}

.btn-clear:hover {
    background: #dc2626;
}

/* Equals Button */
.btn-equals {
    background: var(--success-color);
    color: var(--text-primary);
}

.btn-equals:hover {
    background: #16a34a;
}

/* Function Buttons (Scientific) */
.btn-function {
    background: var(--secondary-color);
    color: var(--text-primary);
    font-size: 0.9rem;
    padding: 14px;
}

.btn-function:hover {
    background: #7c3aed;
}

/* History Panel */
.history-panel {
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    padding: 16px;
    margin-top: 20px;
    border: 1px solid var(--border-color);
    max-height: 200px;
    overflow: hidden;
}

.history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 12px;
}

.history-header h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 8px;
}

.history-header h3 i {
    color: var(--primary-color);
}

.clear-history-btn {
    background: transparent;
    border: none;
    color: var(--text-muted);
    font-size: 0.8rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 4px;
    padding: 4px 8px;
    border-radius: var(--radius-sm);
    transition: all 0.2s ease;
}

.clear-history-btn:hover {
    color: var(--danger-color);
    background: rgba(239, 68, 68, 0.1);
}

.history-list {
    max-height: 120px;
    overflow-y: auto;
}

.history-list::-webkit-scrollbar {
    width: 4px;
}

.history-list::-webkit-scrollbar-track {
    background: var(--bg-tertiary);
    border-radius: 2px;
}

.history-list::-webkit-scrollbar-thumb {
    background: var(--text-muted);
    border-radius: 2px;
}

.empty-history {
    color: var(--text-muted);
    font-size: 0.9rem;
    text-align: center;
    padding: 20px 0;
}

.history-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 8px 0;
    border-bottom: 1px solid var(--border-color);
    cursor: pointer;
    transition: background 0.2s ease;
}

.history-item:last-child {
    border-bottom: none;
}

.history-item:hover {
    background: rgba(99, 102, 241, 0.1);
    margin: 0 -8px;
    padding: 8px;
    border-radius: var(--radius-sm);
}

.history-expression {
    color: var(--text-secondary);
    font-size: 0.85rem;
}

.history-result {
    color: var(--primary-color);
    font-weight: 600;
    font-size: 0.95rem;
}

/* Shortcuts Info */
.shortcuts-info {
    text-align: center;
    margin-top: 16px;
}

.shortcuts-info p {
    color: var(--text-muted);
    font-size: 0.8rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
}

/* Footer */
.footer {
    text-align: center;
    margin-top: 24px;
    padding-top: 16px;
    border-top: 1px solid var(--border-color);
}

.footer p {
    color: var(--text-secondary);
    font-size: 0.85rem;
}

.footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
}

.footer a:hover {
    text-decoration: underline;
}

.footer .fa-heart {
    color: var(--danger-color);
}

/* Responsive */
@media (max-width: 420px) {
    .container {
        padding: 0;
    }

    .calculator {
        border-radius: 0;
        padding: 16px;
    }

    .btn {
        padding: 16px;
        font-size: 1.1rem;
    }

    .current-operand {
        font-size: 2rem;
    }

    .scientific-buttons {
        grid-template-columns: repeat(3, 1fr);
    }

    .btn-function {
        font-size: 0.8rem;
        padding: 12px;
    }
}

/* Animation */
@keyframes buttonPress {
    0% { transform: scale(1); }
    50% { transform: scale(0.95); }
    100% { transform: scale(1); }
}

.btn.pressed {
    animation: buttonPress 0.1s ease;
}

/* Error State */
.display.error .current-operand {
    color: var(--danger-color);
}